PART I

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HARVARD PSYCHOLOGICAL

STUDIES

EDITED BY

HUGO MÜNSTERBERG

Volume II

BOSTON AND NEW YORK

HOUGHTON, MIFFLIN AND COMPANY

The Riverside Press, Cambridge

1906

COPYRIGHT 1906

BY THE PRESIDENT AND FELLOWS OF HARVARD COLLEGE

ALL RIGHTS RESERVED

_Published June 1906_

CONTENTS

EMERSON HALL: Hugo Münsterberg.

I. Experimental Psychology in Harvard 3

II. The Need for Emerson Hall 8

III. Emerson as Philosopher 16

IV. The Place of Experimental Psychology 31

V. The Psychological Laboratory in Emerson Hall 34

OPTICAL STUDIES.

Stereoscopic Vision and the Difference of Retinal Images: G. V.

Hamilton 43

Eye-Movements during Dizziness: E. B. Holt 57

Vision during Dizziness: E. B. Holt 67

Visual Irradiation: Foster Partridge Boswell 75

FEELING.

The Expression of Feelings: F. M. Urban 111

The Mutual Influence of Feelings: John A. H. Keith 141

The Combination of Feelings: C. H. Johnston 159

The Æsthetics of Repeated Space Forms: Eleanor Harris Rowland 193

The Feeling-Value of Unmusical Tone-Intervals: L. E. Emerson 269

ASSOCIATION, APPERCEPTION, ATTENTION.

Certainty and Attention: Frances H. Rousmaniere 277

Inhibition and Reënforcement: Louis A. Turley 293

The Interference of Optical Stimuli: H. Kleinknecht 299

Subjective and Objective Simultaneity: Thomas H. Haines 309

The Estimation of Number: C. T. Burnett 349

Time-Estimation in its Relations to Sex, Age, and Physiological

Rhythms:

Robert M. Yerkes and F. M. Urban 405

Associations under the Influence of Different Ideas: Bird T.

Baldwin 431

Dissociation: C. H. Toll 475

MOTOR IMPULSES.

The Accuracy of Linear Movement: B. A. Lenfest 485

The Motor Power of Complexity: C. L. Vaughan 527

ANIMAL PSYCHOLOGY.

The Mutual Relations of Stimuli in the Frog _Rana Clamata_ Daudin:

Robert M. Yerkes 545

The Temporal Relations of Neural Processes: Robert M. Yerkes 575

The Mental Life of the Domestic Pigeon: John E. Rouse 581

Reactions of the Crayfish: J. Carleton Bell 615

PLATES

_Frontispiece_ 3

I 60

II 64

III 78

IV 80

V 269

VI 271

VII 273

VIII 293

IX 295

EMERSON HALL

[Illustration: HARVARD PSYCHOLOGICAL LABORATORY]

EMERSON HALL

BY HUGO MÜNSTERBERG

I. EXPERIMENTAL PSYCHOLOGY IN HARVARD

On the 27th of December, 1905, Harvard University opened its new house

of philosophy, Emerson Hall. The presence of the American Philosophical

and Psychological Associations gave national significance to the

completion of this building.

The psychologist will find quarters in all parts of Emerson Hall. The

general courses in psychology will be held on the first floor in the

large lecture-room, which has nearly four hundred seats; and close by

are the psychological seminary-room and smaller lecture-rooms for the

advanced psychological courses. On the second floor the psychologist

finds his special library as a wing of the large library hall. But

the exclusive domain of the psychologist is the third floor,--a

psychological laboratory with twenty-five rooms. A large attic hall for

laboratory purposes on the fourth floor completes the psychologist's

allotment.

The work to be reported in future in the Harvard Psychological Studies

will be work done in this new building, and while the researches

reported in the following pages were completed in the smaller quarters

of the old laboratory, it seems natural that this volume, which appears

at this new epoch of our work, should give an account both of our

psychological past and of the development and purpose of Emerson Hall.

The Harvard Psychological Laboratory was founded in 1891 by Professor

William James, who had introduced some experimental features into his

psychological lecture courses for some time before the formal opening

of a regular workshop. Professor James started with two large rooms

on the second floor of Dane Hall, and secured an excellent equipment,

especially for the study of the psychology of the senses. He was

assisted by Dr. Herbert Nichols, and at once gathered a number of

graduate students for research.

In the following year Professor James withdrew from the experimental

work, and the conduct of the laboratory was given over to me. In the

years which followed, Dr. Arthur Pierce, Dr. J. E. Lough, and Dr.

Robert MacDougall were the assistants until three years ago, when the

development of the laboratory demanded a division of the assistant

functions; since that time Dr. E. B. Holt has been the assistant for

the work in human psychology, while Dr. R. M. Yerkes has had charge

of the work in comparative psychology. Since from the first I laid

special emphasis on research work, a greater number of small rooms

was soon needed. In the year 1893, we divided a part of the adjacent

lecture-room into four rooms for special investigations, and two years

later the larger of the two original rooms was divided into five. As

the lecture-room also was finally made part of the research laboratory,

we had at last eleven rooms in Dane Hall. The activities of the

laboratory, however, went far beyond the research work. We had regular

training-courses in experimental practice, and the lecture courses in

human and in comparative psychology drew largely on the resources of

our instrument cases. Yet the original investigations absorbed the

main energy of the laboratory, and demanded a steady expansion of

its apparatus. An illustrated catalogue of the instruments has been

published as part of the Harvard Exhibition at the Chicago World's Fair.

The participation of the students has been controlled by a principle

which has characterized our Harvard work through all these years,

and distinguished it from the methods of most other institutions. I

insist that no student shall engage in one investigation only, but

that every one who has charge of a special problem shall give to

it only half of his working time, while in the other half he is to

be subject in four, five, or more investigations by other members

of the laboratory. In this way each research is provided with the

desirable number of subjects, and all one-sidedness is avoided. Every

experimenter thus comes in contact with a large range of problems and

gets a fair training in manifold observations, besides the opportunity

for concentration on a special research. It is true that this demands

a complicated schedule and careful consideration of the special needs

of every research, but it gives to the work a certain freshness and

vividness, and banishes entirely the depression which is unavoidable

whenever a student is for any length of time a passive subject in one

psychological enquiry only. In both capacities, as experimenter and

as observing subject, only graduate students have been acceptable. In

this way about _one hundred investigations_ on human psychology have

been carried on, for most of which I have proposed the problems and

the special lines of work, taking care that the research of succeeding

years and of succeeding generations of graduate students should show

a certain internal continuity. Whenever the results seemed fit for

publication, the papers have been published under the names of the

students who had the responsibility for the conduct of the experiments.

Until three years ago the publication was scattered; most of the

papers, however, appeared in the Psychological Review. The Harvard

Psychological Studies, beginning in 1903, are to gather the bulk of our

material, although not a few of the researches of recent years have

been published in other places.

The laboratory has always sought to avoid one-sidedness, and this the

more as it was my special aim to adjust the selection of topics to the

personal equations of the students, many of whom came with the special

interests of the physician, the zoölogist, the artist, the pedagogue,

and so on. My own special interests may have emphasized those problems

which refer to the motor functions and their relations to attention,

apperception, space-sense, time-sense, feeling, etc. At the same time

I have tried to develop the psychological-æsthetic work, which has

become more and more a special branch of our laboratory, and there has

been no year in which I have not insisted on some investigations in the

fields of association, memory, and educational psychology. On the other

hand, in a happy supplementation of interests, Dr. Holt has emphasized

the physiological psychology of the senses, and Dr. Yerkes has quickly

developed a most efficient experimental department of animal psychology.

As the work thus became more manifold, the old quarters in Dane Hall

appeared less and less sufficient. And yet this laboratory development

has been merely parallel to the growth of general philosophical studies

in the whole University. The demand for a new hall, exclusively devoted

to philosophy, was thus suggested from many sides. The idea of linking

it with the name of Ralph Waldo Emerson has been for years a cherished

plan of Professor Palmer.

An especially appropriate time for the realization of such a plan came

in the approach of the hundredth anniversary of Emerson's birthday.

Almost two years before this date the Department took the first steps

in seeking to interest the members of the Visiting Committee for the

collection of the necessary funds. This Committee, consisting of Mr.

G. B. Dorr, chairman, Mr. R. H. Dana, Dr. R. Cabot, Mr. J. Lee, Mr.

D. Ward, and Mr. R. C. Robbins, showed not only warm interest, but

lent itself to the furtherance of the plans with such an energy and

devotion that the Philosophical Department owes to these friends of

philosophy in Harvard the most lasting gratitude. Various means were

taken by the Committee and by the Department to stir the interest of

the public, and soon the gifts began to come in, gifts of which some

were clearly given from sympathy with the work of the Philosophical

Department, some evidently in memory of Emerson. The original plans

of the architect called for $150,000 for the building. When, on the

25th of May, 1903, the hundredth anniversary of Emerson's birthday was

celebrated, the University had contributions amounting to more than

this sum, and given by one hundred and seventy persons.

It was soon found, however, that this sum was inadequate; yet we never

asked in vain. Additional gifts came in for the building fund, just as

later the generosity of several friends furnished the building with a

handsome equipment and the laboratory with new instruments. Mr. R. C.

Robbins gave the books for a philosophical library to be placed in the

new Hall.

The architect chosen was Mr. Guy Lowell, who has had to labor under the

difficulties involved in the fact that the best and quietest available

place was on Quincy Street opposite Robinson Hall. This spot demanded

that the new building be harmonized with Robinson and Sever Halls, two

structures most unlike in their architectural style. There was not

even the possibility of making it a companion to Robinson Hall, since

the latter has but two stories, while it was evident that Emerson

Hall needed three stories. The plan finally accepted, a Greek, brick

building with brick columns and rich limestone trimmings, provided for

the work of the whole Philosophical Division with the exception of

education. The Education Department, with its large library, will soon

need a whole building of its own, and has thus had no interest in being

housed under the roof of Emerson Hall. On the other hand, the building

was to give full space to that part of our Philosophical Division which

now forms, like education, an administrative unity,--the Department of

Social Ethics. A special library, museum rooms, etc., for social ethics

were planned for the second floor by the munificence of an anonymous

benefactor. Altogether we have six large lecture-rooms, two library

halls, two collection-rooms, a department-room, a seminary-room,

two studies and conference-rooms, twenty-five laboratory-rooms, all

connected by very spacious, well-lighted halls and broad, imposing

stairways. Surely never before in the history of scholarship has such

a stately house been built for philosophy. And while the nature of the

work is certainly not determined by the luxury of stone and carved

wood, teachers and students alike must feel these superb surroundings

as a daily stimulus to their best efforts.

At Christmas, 1905, the building stood ready for use, and Duveneck's

bronze statue of Emerson was unveiled in the entrance hall. At the

opening meeting, after short dedicatory orations by President Eliot

and Dr. Edward Emerson, a real exchange of ideas in a joint debate

of the Philosophical and Psychological Associations was substituted

for the usual formal exercises. The question debated was suggested by

the fact that Emerson Hall was to house the psychological laboratory.

Does psychology really belong to philosophy or rather to the natural

sciences? As the representative of Harvard, it was my part to open the

debate and to characterize the attitude of the Harvard laboratory.

My remarks on that occasion may thus serve as the most direct

introduction to our work. They are printed here, together with a short

sketch of the equipment of the laboratory. I venture to add also two

other papers, one of which points to the administrative, the other and

longer one to the philosophical background of Emerson Hall. Inasmuch

as I was Chairman of the Philosophical Department throughout the five

years in which the plan for Emerson Hall was growing and became finally

realized, it has been my official duty repeatedly to express our hopes

and ideals. Thus I had to formulate the wishes of the Department at

the outset in a letter to the Visiting Committee, a letter which was

used as a circular in asking the public for funds. Two years later when

Harvard celebrated the Emerson anniversary, I delivered an address on

Emerson as philosopher. This epistemological paper may seem far removed

from the interests of the Harvard Psychological Studies, and yet I am

glad to print it in this laboratory volume, and thus emphatically to

indicate that I for one consider philosophy the true basis for the

psychologist.

There follow thus, first, the letter to the Visiting Committee, with

which the Emerson Hall movement took its official inception in 1901;

secondly, the address delivered at Harvard on the celebration of the

Emerson anniversary in May, 1903; thirdly, the paper contributed to the

debate of the philosophers at the opening meeting in December, 1905;

and, finally, a description of the present status of the laboratory in

January, 1906.

II. THE NEED FOR EMERSON HALL

[The letter addressed to the Visiting Committee of the Overseers of

Harvard University, in 1901, reads as follows:]

Gentlemen,--The philosophical work in Harvard has in the last twenty

years gone through an inner development which has met with a hearty

response alike on the part of the University and of the students. The

students have attended the courses in constantly growing numbers, the

Governing Boards have provided the Division amply with new teachers,

steadily increasing the number of professors, instructors, and

assistants. The outer growth of the Division has thus corresponded

most fortunately to the internal development, by an harmonious

coöperation of the administration, the teachers, and the students of

the University. And yet there remains one other factor as an essential

condition for the healthy life of the Department, a factor which cannot

be provided by the University itself and for which the help must come

from without. Our work needs a dignified home where under one roof all

the varied philosophical work now carried on at Harvard may be united.

The need has been urgently felt for many years, but only with the

recent growth has the situation become intolerable. It is therefore the

unanimous opinion of the Department that we must ask the public for the

funds to build at Harvard a "School of Philosophy," in the interest of

the students and of the teachers, in the interest of the Department and

of the University, in the interest of culture and of scholarship.

The present work of the Division of Philosophy can be indicated by

a few figures. We entered the current year with a teaching-staff of

six full professors, two assistant professors, four instructors, two

teaching-fellows, and six assistants. The instruction of these twenty

men covers the ground of history of philosophy, metaphysics, theory

of knowledge, psychology, logic, ethics, æsthetics, philosophy of

religion, philosophy of science and sociology. Thirty-two courses

have been offered. These courses are grouped in three classes: the

introductory courses, intended primarily for Sophomores and Juniors;

the systematic and historic courses, planned for Juniors, Seniors,

and Graduates; and the research courses for Graduates only. But

the students whom we try to reach differ not only with regard to

their classes, their corresponding maturity, and their degree of

philosophical preparation, but also with regard to the aims and

interests for which they elect philosophical studies in the University.

The one group seeks in our field liberal education. The fundamental

problems of life and reality, and the historic solutions of them

which the great thinkers developed, the values of truth and beauty

and morality, the laws of the mental mechanism and of the social

consciousness, all these promise and prove to be incomparable agencies

for widening the soul and giving to our young men depth, strength, and

ideals. Not a few of the students who belong to this group remain loyal

to philosophy through three or four years. A second group of students

need our courses as preparation for divers scholarly or practical

aims. The future lawyer, teacher, physician, minister, scientist, or

philanthropist knows that certain courses in ethics or psychology, in

education or logic afford the most solid foundations for his later

work; there is hardly a course in our Division which is not adjusted to

some kind of professional study. The third group finally, naturally the

smallest, but to the teachers the most important, consists of those to

whom philosophy itself becomes a life's work. The Harvard Department

believes that there is nowhere else in this country or abroad such

an opportunity for systematic and all-round training for an advanced

student of philosophy as is offered here, covering easily a man's full

work for six years, advancing from the introductory courses of the

Sophomore year to the six seminaries of the graduate years and finally

reaching the doctor's thesis in the third year after graduation.

The extent to which the Harvard students make use of these

opportunities is to be inferred from the figures which the last Annual

Report of the President offers. These refer to the year 1899-1900; the

current year will show somewhat the same proportions, perhaps even

an increase of graduate work. The figures are necessarily too low,

inasmuch as they refer merely to those students who take examinations

in the courses and omit those who merely attend the lectures. The

attendance in the philosophical courses was last year over one thousand

students. They belonged to all parts of the University, 188 Graduates,

210 Seniors, 218 Juniors, 175 Sophomores, 59 Specials, 57 Scientifics,

55 Divinity students, and the rest from the Freshman class, the Law

School, and the Medical School. The introductory courses were attended

by almost four hundred students, that is, by a number corresponding to

the size of the Junior class. As, in spite of natural fluctuations,

this figure is pretty constant,--in 1897 reaching its maximum with

427,--it can be said that in Harvard under the system of absolutely

free election practically every student who passes through Harvard

required of himself at least a year of solid philosophical study.

An even higher interest, however, belongs to the figures which refer

to the most advanced courses offered, especially to the courses of

research. It has always been the most characteristic feature of the

Harvard Philosophical Department to consider the advancement of

knowledge as its noblest function. The productive scholarship of the

Department is shown by the fact that the last two years alone brought

before the public eight compendious scholarly works from members of our

Department, besides a large number of smaller contributions to science.

To train also in the students this highest scholarly attitude, that

of the critical investigator as contrasted with that of the merely

receptive hearer of lectures, is thus the natural aim of our most

advanced work; it is this spirit which has given to the Department its

position in the University and in the whole country. This prevalence

of the spirit of research is the reason why, as the Report of the Dean

of the Graduate School points out, the Philosophical Department has a

larger number of graduate students who have carried on graduate studies

elsewhere than any other Department of the University. The table of

the Dean which records these migrating graduate students who come to

us for advanced work after graduate studies at other universities,

is as follows: Mathematics 6, Natural History 7, Political Science

7, Modern Languages 11, Classics 14, History 15, English Literature

16, Philosophy 20. If we consider the whole advanced work of the

University, that is the totality of those courses which are announced

as "primarily for Graduates," we find that the following number of

graduate students, including the graduate members of the professional

schools, have taken part: Classics 103, Philosophy 96, English 75,

German 61, History and Government 52, Romance Languages 45, Mathematics

39, Economics 23, Chemistry 21, in the other departments less than

twenty. But this situation turns still more strongly in favor of

philosophy as soon as we consider the technical research courses, those

which in the language of the catalogue are known as the 20-courses, and

omit those graduate courses which are essentially lecture courses. In

these research courses the number of Graduate Students is: Philosophy

71, History and Government 34, Chemistry 13, Zoölogy 12, Geology 10,

and in the other departments less than ten.

These few figures may be sufficient to indicate not only the extent

of the Department and its influence, but above all the harmonious

character of this development. The most elementary courses, the solid

routine courses, and the most advanced courses, show equal signs of

growth and progress, and the whole work with its many side branches

remains a well-connected unity with a clear systematic plan. All this

must be understood before one can appreciate the striking contrast

between the work and the workshop. It is of course easy to say at once

that the truth of a metaphysical thought does not depend upon the

room in which it is taught, and that the philosopher is not, like a

physicist or chemist, dependent upon outer equipments. Yet, this is but

half true, and the half of the statement which is false is of great

importance.

The dependence upon outer conditions is perhaps clearest in the case

of psychology, which has been for the last twenty-five years an

objective science with all the paraphernalia of an experimental study:

the psychologist of to-day needs a well-equipped laboratory no less

than the physicist. Harvard has given the fullest acknowledgment to

this modern demand and has spent large sums to provide the University

with the instruments of an excellent psychological laboratory; the

one thing which we miss is room, simply elbow-room. Our apparatus is

crowded in the upper story of Dane Hall, and even that small story

must give its largest room for the lectures of other departments and

another room to a philosophical reading-room. The space which remains

for the psychological work is so absolutely out of proportion to the

amount of work going on that the problem how to bring all the men into

those few rooms has become the most difficult of all our laboratory

problems. During the current year, besides the training-courses,

twenty-three men are engaged there in original research, each one with

a special investigation and each one anxious to devote as much time as

possible to his research; only the most complicated adjustment makes

it possible at all, and yet the mutual disturbance, the necessity of

passing through rooms in which other men are working, and of stopping

the work when other men need the place interfere every day with the

success of the instruction. A mechanical workshop is an urgent need of

our laboratory, and yet we cannot afford the room; and while the only

desirable arrangement would be to have the psychological lectures in

the same building where the apparatus is stored,--as the instruments

are necessary for the experimental demonstrations,--there is no room

for the lectures under the roof of Dane Hall, which houses the Bursar's

Office and Coöperative Stores. The result is that the instruments

must be carried through the yard in rain or shine, an effective way

to damage our valuable equipment. But the evils connected with the

present locality of the psychological laboratory are not only such

as result from its narrowness. Its position on Harvard Square, with

the continuous noise and the vibration of the ground, is perfectly

prohibitory for large groups of psychological studies and disturbing

for every kind of work for which concentration of attention is a

fundamental condition. Finally a psychological laboratory, perhaps

still more than a physical one, needs in its whole construction a

perfect adaptation to its special purpose; the walls, the shape, and

the connection of the rooms, everything must be built, as has been

done in other universities, for the special end. We have merely the

rooms of the old Law School with thin partitions dividing them. In

short everything is in a state which was tolerable during the last few

years only because it was felt as provisional, but the time when the

psychological laboratory must have really adequate quarters cannot be

postponed much longer.

The needs of the psychological work can thus be easily demonstrated to

every beholder; but while perhaps less offensive on the surface, the

outer conditions of the other branches of the Philosophical Department

are not therefore less unsatisfactory. The advanced student of logic

or ethics does not need a laboratory, but he needs seminary-rooms with

a working library where his work may have a local centre, where he

can meet his instructors and his fellow students engaged in related

researches, where he may leave his books and papers. To-day all this

theoretical work has no home at all; the seminaries seek refuge in

an empty room of the laboratory at a late evening hour, in a chance

lecture-room, or in private homes; there is nowhere continuity, no

place to collect or to deposit, no opportunity to meet beyond official

hours, no feeling of coherence suggested by surroundings. The most

advanced research work of the country is thus done under external

conditions which suggest the spirit of a schoolroom, conditions which

deprive students and instructors equally of the chance to make our

seminaries the fitting forms for their rich content. But if all this is

most deeply felt by the advanced students, it is not less true and not

less deplorable for the undergraduate courses. There is nowhere fixity

of association between the work and the room. The philosophy courses

are scattered over the whole yard, wandering each year from one quarter

to the other, creeping in wherever a vacant room can be found, not even

the instructors knowing where their nearest colleagues are meeting

students. The dignity and the unity of the work are equally threatened

by such a state of affairs. There remains not even a possibility for

the instructor to meet his students before or after the lecture; his

room is filled up to the time when he begins and a new class rushes

in before he has answered questions. A business-like restlessness

intrudes into the instruction, and yet philosophy above all needs a

certain repose and dignity.

Thus what we need is clear. We need a worthy monumental building at a

quiet central spot of the Harvard yard, a building which shall contain

large and small lecture-rooms, seminary-rooms, a reading-room, and

one whose upper story shall be built for a psychological laboratory,

so that under one roof all the philosophical work, metaphysical

and ethical, psychological and logical, may be combined. Here the

elementary and the advanced work, the lecture courses and the

researches, the seminaries and the experiments, the private studies in

the reading-room and the conferences and meetings of the assistants

would go on side by side. Here would be a real school of philosophy

where all Harvard men interested in philosophy might find each other

and where the students might meet the instructors.

Such a home would give us first, of course, the room and the

external opportunities for work on every plane; it would give us

also the dignity and the repose, the unity and the comradeship of a

philosophical academy. It would give us the inspiration resulting from

the mutual assistance of the different parts of philosophy, which

in spite of their apparent separation are still to-day parts of one

philosophy only. All this would benefit the students of philosophy

themselves, but not less good would come to the University as a

whole. The specialization of our age has brought it about that in

the organization of a university, even philosophy, or rather each of

the philosophical branches, has become an isolated study coördinated

with others. The average student looks to psychology as to physics

or botany; he thinks of ethics as he thinks of economics or history;

he hears about logic as coördinated with mathematics, and so on. The

University has somewhat lost sight of the unity of all philosophical

subjects and has above all forgotten that this united philosophy is

more than one science among other sciences, that it is indeed the

central science which alone has the power to give inner unity to the

whole university work. Every year our universities reward our most

advanced young scholars of philology and history, of literature and

economics, of physics and chemistry, of mathematics and biology with

the degree of Ph.D., that is of Doctor Philosophiae, thus symbolically

expressing that all the special sciences are ultimately only branches

of philosophy; but the truth of this symbol has faded away from the

consciousness of the academic community. All knowledge appears there as

a multitude of scattered sciences and the fact that they all have once

been parts of philosophy, till one after the other has been dismissed

from the mother arms, has been forgotten. A school of philosophy as a

visible unity in the midst of the yard will renew this truth and thus

give once more to the overwhelming manifoldness of intellectual efforts

of our University a real unity and interconnection; the external

connection of administration will be reënforced by the inner unity of

logical interdependence.

The time is ripe for a school of philosophy to play this rôle and to

fulfil again its old historical mission, to be the unifying principle

of human knowledge and life. The second half of the nineteenth century

was essentially controlled by realistic energies, by the spirit of

analysis, by the triumph of natural science and technique. But a long

time before the century came to an end a reaction started throughout

the whole intellectual globe; the synthetic energies again came to

the foreground, the idealistic interests were emphasized in the most

different quarters; the historical and social sciences make to-day the

same rapid progress which fifty years ago characterized the natural

sciences, and everywhere in the midst of the empirical sciences

there is awakening again the interest in philosophy. In the days of

anti-philosophical naturalism scientists believed that philosophy

had come to an end and that an unphilosophical positivism might

be substituted for real philosophy; to-day the mathematicians and

physicists, the chemists and biologists, the historians and economists

eagerly turn again and again to philosophy, and on the borderland

between philosophy and the empirical sciences they seek their most

important problems and discussions. The world begins to feel once more

that all knowledge is empty if it has no inner unity, and that the

inner unity can be brought about only by that science which enquires

into the fundamental conceptions and methods of thought with which the

special sciences work, into the presuppositions and ultimate axioms

with which they begin, into the laws of mental life which lie at the

basis of every experience, into the ways of teaching the truth, and

above all into the value of human knowledge, its absolute meaning and

its relation to all the other human values--those of morality, beauty,

and religion. The most advanced thinkers of our time are working to-day

in all fields of knowledge to restore such a unity of human life

through philosophy. To foster this spirit of the twentieth century in

the life of our University there is no more direct way possible than to

give a dignified home to the philosophical work. Such a building ought

to be a Harvard Union for scholarly life.

The beautiful building which we see in our minds should not be

devoted to a single system of philosophy. In its hall we hope to see

as greeting for every student the busts of Plato the Idealist and

Aristotle the Realist, of Descartes and Spinoza, of Bacon and Hobbes,

of Locke and Hume and Berkeley, of Kant and Fichte and Hegel, of Comte

and Spencer, of Helmholtz and Darwin. The School of Philosophy will

be wide open to all serious thought, as indeed the members of the

Department to-day represent the most various opinions and convictions.

This ought never to be changed; it is the life-condition of true

philosophy. Yet there is one keynote in all our work: a serious,

critical, lofty idealism which forms the background of the whole

Department and colors our teaching from the elementary introductions

to the researches of our candidates for the doctor's degree. All the

public utterances which have come from the Department in recent years

are filled with this idealism, in spite of the greatest possible

variety of special subjects and special modes of treatment. Here belong

The Will to Believe and the Talks to Teachers, by William James, the

Noble Lectures and the Glory of the Imperfect, by George Herbert

Palmer, Poetry and Religion, by George Santayana, The Principles of

Psychology, and Psychology and Life, by Hugo Münsterberg, Jesus Christ

and the Social Question, by Francis Peabody, Educational Aims and

Educational Values, by Paul Hanus, Shaftesbury, by Benjamin Rand, the

Conception of God, and The World and the Individual, by Josiah Royce.

We have sought a name which might give symbolic expression to this

underlying sentiment of idealism and might thus properly be connected

with the whole building. It cannot be that of a technical philosopher.

Such a name would indicate a prejudice for a special system of

philosophy, while we want above all freedom of thought. It ought to be

an American, to remind the young generation that they do not live up

to the hopes of the School of Philosophy if they simply learn thoughts

imported from other parts of the world, but that they themselves as

young Americans ought to help the growth of philosophical thought. It

ought to be a Harvard man--a man whose memory deserves that his name

be daily on the lips of our students, and whose character and whose

writing will remain a fountain of inspiration. Only one man fulfils all

these demands perfectly: Ralph Waldo Emerson. It is our wish and hope

that the new, dignified, beautiful home of philosophy may soon rise as

the moral and intellectual centre of Harvard University and that over

its doors we shall see the name: Emerson Hall--School of Philosophy.

III. EMERSON AS PHILOSOPHER

[The following address was delivered at Harvard University, May,

1903, as part of the Emerson Celebration:]

At the hundredth anniversary of Emerson's birthday, Harvard University

is to take a noble share in the celebration. For years it has been one

of the deepest desires of the Harvard community to erect in the college

yard a building devoted to philosophy only. To-day this building is

secured. To be sure, the good-will of the community must still do much

before the funds allow the erection of a building spacious enough to

fulfil our hopes; but whether the hall shall be small or large, we know

to-day that it will soon stand under the Harvard elms and that over

its door will be inscribed the name: Ralph Waldo Emerson. No worthier

memorial could have been selected. Orations may be helpful, but the

living word flows away; a statue may be lasting, but it does not awaken

new thought. We shall have orations and we shall have a statue, but

we shall have now, above all, a memorial which will last longer than

a monument and speak louder than an oration: Emerson Hall will be a

fountain of inspiration forever. The philosophical work of Harvard

has been too long scattered in scores of places; there was no unity,

philosophy had no real home. But Emerson Hall will be not only the

workshop of the professional students of philosophy, will be not only

the background for all that manifold activity in ethics and psychology,

in logic and metaphysics, in æsthetics and sociology, it will become

a new centre for the whole University, embodying in outer form the

mission of philosophy to connect the scattered specialistic knowledge

of the sciences. Harvard could not have offered a more glorious gift to

Emerson's memorial.

But the spirit of such a memorial hour demands, more than all,

sincerity. Can we sincerely say that the choice was wise, when we look

at it from the point of view of the philosophical interests? It was

beautiful to devote the building to Emerson. Was it wise, yes, was it

morally right to devote Emerson's name to the Philosophy Building?

Again and again has such a doubt found expression. Your building, we

have heard from some of the best, belongs to scientific philosophy; the

men who are to teach under its roof are known in the world as serious

scholars, who have no sympathy with the vague pseudo-philosophy of

popular sentimentalists; between the walls of your hall you will have

the apparatus of experimental psychology, and you will be expected to

do there the most critical and most consistent work in methodology

and epistemology. Is it not irony to put over the door, through which

daily hundreds of students are to enter, the name of a man who may be

a poet and a prophet, a leader in literature and a leader in life,

but who certainly was a mystic and not a thinker, an enthusiast but

not a philosopher? Not only those who belittle him to-day and who

short-sightedly deny even his immense religious influence, but even

many of Emerson's warmest admirers hold such an opinion. They love

him, they are inspired by the superb beauty of his intuitions, but

they cannot respect the content of his ideas, if they do not wish to

deny all their modern knowledge and scientific insight. Yes, for the

most part they deny that his ideas form at all a connected whole;

they are aphorisms, beautiful sparks. Did he not himself say: "With

consistency a great soul has simply nothing to do. He may as well

concern himself with his shadow on the wall." And yet how can there

be philosophy without consistency; how can we interpret reality if we

contradict ourselves? If Emerson's views of the world did really not

aim at consistency and did really ignore our modern knowledge, then

it would be better to go on with our philosophical work in Harvard

without shelter and roof than to have a hall whose name symbolizes both

the greatest foe of philosophy, the spirit of inconsistency, and the

greatest danger for philosophy, the mystic vagueness which ignores real

science.

But Emerson stands smiling behind this group of admirers and says,

"To be great is to be misunderstood." Yes, he did say, "A foolish

consistency is the hobgoblin of little minds, adored by little

statesmen and philosophers and divines;" but he soon adds, "Of one

will the actions will be harmonious however unlike they seem." Emerson

despises the consistency of the surface because he holds to the

consistency of the depths, and every sentence he speaks is an action of

the one will, and however unlike they seem they are harmonious, and, we

can add, they are philosophical; and, what may seem to these anxious

friends more daring, they are not only in harmony with each other,

they are in deepest harmony with the spirit of modern philosophy, with

a creed which ought to be taught by the most critical scholars of

Harvard's Philosophy Hall.

What is the essence of Emerson's doctrine in the realm of philosophy?

It seems like sacrilege to formulate anything he said in the dry terms

of technical philosophy. We must tear from it all the richness and

splendor of his style, we must throw off the glory of his metaphor, and

we must leave out his practical wisdom and his religious emotion. It

seems as if we must lose all we love. It is as if we were to take a

painting of Raphael and abstract not only from the richly colored gowns

of the persons in it, but from their flesh and blood, till only the

skeletons of the figures remained. All beauty would be gone, and yet we

know that Raphael himself drew at first the skeletons of his figures,

knowing too well that no pose and no gesture is convincing, and no

drapery beautiful if the bones and joints fit not correctly together.

And such a skeleton of theoretical ideas appears not only without

charm, it appears necessarily also uninteresting, without originality,

commonplace. All the philosophies, from Plato to Hegel, brought down to

their technical formulas, sound merely like new combinations of trivial

elements, and yet they have made the world, have made revolutions and

wars, have led to freedom and peace, have been mightier than traditions

and customs; and it is true for every one of them that, as Emerson

said, "A philosopher must be more than a philosopher."

There are, it seems, three principles of a philosophical character

without which Emerson's life-work cannot be conceived. To bring

them to the shortest expression we might say, Nature speaks to us;

Freedom speaks in us; the Oversoul speaks through us. There is no

word in Emerson's twelve volumes which is inconsistent with this

threefold conviction, and everything else in his system either follows

immediately from this belief or is a non-essential supplement. But

that threefold faith is a courageous creed indeed. The first, we said,

refers to Nature; he knew Nature in its intimacy, he knew Nature in

its glory; "Give me health and a day and I will make the pomp of

emperors ridiculous." And this Nature, that is the assertion, is not

what natural sciences teach it to be. The Nature of the physicist, the

dead world of atoms controlled by the laws of a dead causality, is not

really the Nature we live in; the reality of Nature cannot be expressed

by the record of its phenomena, but merely by the understanding of its

meaning. Natural science leads us away from Nature as it really is. We

must try to understand the thoughts of Nature. "Nature stretches out

her arms to embrace man; only let his thoughts be of equal greatness;"

and again Emerson says, "All the facts of natural history taken by

themselves have no value, but are barren like a single sex; but

marry it to human history and it is full of life;" and finally, "The

philosopher postpones the apparent order of things to the empire of

Thought."

And in the midst of Nature, of the living Nature, we breathe in

freedom; man is free. Take that away and Emerson is not. Man is free.

He does not mean the freedom of the Declaration of Independence, a

document so anti-Emersonian in its conception of man; and he does not

mean the liberty after which, as he says, the slaves are crowing while

most men are slaves. No, we are free as responsible agents of our

morality. We are free with that freedom which annuls fate; and if there

is fate, then freedom is its most necessary part. "Forever wells up the

impulse of choosing and acting in the soul." "So far as man thinks he

is free." "Before the revelations of the soul, time, space, and nature

shrink away." "Events are grown on the same stem with the personality;

they are sub-personalities." "We are not built like a ship to be

tossed, but like a house to stand." This freedom alone gives meaning to

our life with its duties, and puts the accent of the world's history on

the individual, on the personality: "All history resolves itself very

easily into the biography of a few stout and earnest persons," and "An

institution is the lengthened shadow of a man."

Nature speaks to us, Freedom speaks in us, but through us speaks a Soul

that is more than individual, an over-individual soul, an "Oversoul,

within which every man is contained and made one with all others."

Now even "Nature is a great shadow, pointing always to the sun behind

her." Every one of us belongs to an absolute consciousness which in us

and through us wills its will; "Men descend to meet" and "Jove nods to

Jove from behind each of us." Yes, "Man is conscious of a universal

soul within or behind his individual life, wherein as in a firmament

justice, truth, love, freedom arise and shine." The ideals, the duties,

the obligations, are not man's will but the will of an Absolute.

Does not all this sound like a wilful denial of all that has been fixed

by the sciences of our time? Does not every Sophomore who has had his

courses in Physics, Psychology, and Sociology know better? He knows,

we all know, that the processes of Nature stand under physical laws,

that the will of man is the necessary outcome of psychological laws,

that the ideals of man are the products of human civilization and

sociological laws. And if every atom in the universe moves according

to the laws which physics and chemistry, astronomy and geology, have

discovered, is it not anti-scientific sentimentality to seek a meaning

and thoughts in the mechanical motions of the dead world of substance?

So the poet may speak, but we ought not to say that his fanciful dreams

have value for scholarly philosophers. The philosophy of the scientist

ought to be the acknowledgment that matter and energy, and space and

time are eternal, and that the smallest grain of sand and the largest

solar system move meaningless by blind causality.

And emptier still is the naïve belief that man is free. Do we not

profit from decades of psychological labor, whereby the finest

structure of the brain has been discovered, wherein the psychological

laws have been studied with the exactitude of a natural science,

wherein we have studied the mental life of animals and children, and

have observed the illusions of freedom in the hypnotized man and in

the insane? Yes, we know to-day that every mental act, that every

psychological process is the absolutely necessary outcome of the given

circumstances; that the functions of the cells in the cortex of the

brain determine every decision and volition, and that man's deed is as

necessary as the falling of the stone when its support is taken away.

Yes, modern psychology does not even allow the will as an experience of

its own kind; it has shown with all the means of its subtle analysis

that all which we feel as our will is only a special combination of

sensations which accompany certain movement-impulses in our body. Can

we still take it seriously, when the philosopher steps in and pushes

sovereignly aside all the exact knowledge of mankind, and declares

simply "Man's will is free!"

Finally, the claim for the over-personal, absolute consciousness in

man. It is a triumph of modern science to understand how the duties and

ideals have grown up in the history of civilization. What one nation

calls moral is perhaps indifferent or immoral for another people or

for another time; what the one calls beautiful is ugly for the other;

what one period admires as truth is absurdity for another; there is no

absolute truth, no absolute beauty, no absolute religion, no absolute

morality; and sociology shows how it was necessary that just these

ideals and just these obligations should have grown up under a given

climate and soil, a given temperament of the race, a given set of

economical conditions, a given accumulation of technical achievements.

Man has made his Absolute, not the Absolute made man, and whatever

hopes and fears make men believe, the scholarly mind cannot doubt that

these beliefs and idealizations are merely the products of the feelings

and emotions of individuals bound together by equal conditions of life.

Leave it to the raptures of the mystic to ignore all scientific truth,

to get over-soul connection beyond all experience. In short, to accept

Emerson's philosophy, the scientist would say, means to be a poet where

Nature is concerned, means to be ignorant where man is concerned, and

means to be a mystic where moral and religious, aesthetic and logical

ideals are concerned. Can such be the herald of modern philosophy?

But those who are so proud and so quick are not aware that the times

have changed and that their speech is the wisdom of yesterday. In the

history of human knowledge the periods alternate. Great waves follow

each other, and while one tendency of scientific thought is ebbing,

another is rising; and there is no greater alternation than that

between positivism and idealism. The positivistic period of natural

science has ebbed for ten or fifteen years; an idealistic one is

rising. Emerson once said here in Harvard that the Church has periods

when it has wooden chalices and golden priests, and others when it

has golden chalices and wooden priests. That is true for the churches

of human knowledge too, and for knowledge of all denominations.

Forty, fifty years ago, in the great period when Helmholtz discovered

the conservation of energy and Darwin the origin of species, one

naturalistic triumph followed the other, golden high priests of

natural science were working with wooden chalices in narrow, awkward

laboratories; to-day natural science has golden chalices provided

in luxurious institutions, but there are too many wooden priests.

The fullest energies of our time are pressing on to an idealistic

revival, are bringing about a new idealistic view of the world, and

turning in sympathy to that last foregoing period of idealism of

which Ralph Waldo Emerson was perhaps the last original exponent.

But also with his period idealism was not new. When he came to speak

on the Transcendentalist, he began, "The first thing we have to say

respecting the new views here in New England is that they are not new."

Yes, indeed; since the beginnings of Greek philosophy, more than two

thousand years ago, the two great tendencies have constantly followed

each other. Each one must have its time of development, must reach its

climax, must go over into undue exaggeration, and thus destroy itself

to make room for the other, which then begins in its turn to grow, to

win, to overdo, and to be defeated.

Glorious had been the triumph of Positivism in the middle of the

eighteenth century when the French encyclopædists were at work, those

men who wrote the decrees for the French Revolution. But before the

last consequences of the Positivism of the eighteenth century were

drawn, the idealistic counter-movement had started. Immanuel Kant

gave the signal, he fired the shot heard round the world; and Fichte

followed, whose ethical Idealism changed the map of Europe, and his

spirit went over the Channel to Carlyle, and finally over the ocean to

these shores of New England and spoke with the lips of Emerson. It is

unimportant whether Emerson studied the great transcendental systems

in the original; he knew Kant and Schelling probably at first through

Coleridge, and Fichte through Carlyle. But in the mean time Idealism

too had exaggerated its claims, it had gone forward to Hegel, and

while Hegelian thought, about 1830, held in an iron grasp the deepest

knowledge of his time, his neglect of positive experience demanded

reaction, a counter-movement became necessary, and in the midst of

the nineteenth century the great idealistic movement with all its

philosophical and historical energies went down, and a new Positivism,

full of enthusiasm for natural science and technique and full of

contempt for philosophy, gained the day. With logical consistency,

the spirit of empiricism went from realm to realm. It began with the

inorganic world, passed into physics, then forward to chemistry, became

more ambitious and conquered the world of organisms, and when biology

had said its positivistic say, turned from the outer nature of being

to the inner nature. The mind of man was scrutinized with positivistic

methods; we came to experimental psychology, and finally, as the

highest possible aim of naturalism, to the positivistic treatment of

society as a whole, to sociology. But naturalism again has overdone its

mission, the world has begun to feel that all the technique and all the

naturalistic knowledge makes life not more worth living, that comfort

and bigness do not really mean progress, that naturalism cannot give

us an ultimate view of the world. And above all, the reaction has come

from the midst of the sciences themselves. Twenty years ago scientific

work received its fullest applause for the neglect of philosophical

demands. Ten years ago the feeling came up that there are after all

problems which need philosophy, and to-day philosophers, with good or

bad philosophy, are at work everywhere. The physicists, the chemists

and the biologists, the astronomers and the mathematicians, the

psychologists and the sociologists, the historians and the economists,

the linguists and the jurists, all are to-day busily engaged in

philosophical enquiries, in enquiries into the conditions of their

knowledge, into the presuppositions and methods of their sciences, into

their ultimate principles and conceptions; in short, without a word

of sudden command, the front has changed its direction. We are moving

again towards philosophy, towards Idealism, towards Emerson.

Does all this mean that we are to forget the achievements of natural

science, and ignore the results of empirical labor, of labor which has

given us an invincible mastery of stubborn nature and an undreamed-of

power to calculate all processes of the physical and of the psychical

world? No sane man can entertain such a notion. Yes, such ideas

would contradict the laws which have controlled the alternation

of Idealism and Positivism through the ages of the past. Whenever

Positivism returned, it always showed a new face, and the teaching of

the intervening period of Idealism was never lost. The naturalism of

the middle of the nineteenth century was not at all identical with the

naturalism of the middle of the eighteenth; and so Idealism too, as

often as it returned to mankind after periods of neglect and contempt,

had every time gained in meaning, had every time found increased

responsibilities, had every time to do justice to the new problems

which the preceding period of Positivism had raised. If Idealism

to-day wants to gain new strength, nothing must be lost of all that

the last fifty years have brought us, no step must be taken backward,

the careful scientific work of the specialists must be encouraged and

strengthened, and yet the totality of this work must be brought under

new aspects which allow a higher synthesis; yes, a higher synthesis

is the problem of the philosopher of to-day. He does not want to be

ignorant of natural science and simply to substitute idealistic demands

in the place of solid, substantial facts; and he should feel ashamed

of the foul compromise with which half-thinkers are easily satisfied,

a compromise which allows science its own way till it comes over

the boundaries of human emotions, a compromise which accepts rigid

causality but pierces little holes in the causal world, making little

exceptions here and there that human freedom may be saved in the midst

of a world-machinery; a compromise which accepts the social origin

of ideals, but claims a mystic knowledge that just our own private

pattern will remain in fashion for eternity. No philosophy can live

by compromises. If natural science is to be accepted and Idealism is

to hold its own, they must be combined, they must form a synthesis in

which the one no longer contradicts the other. Just such synthetic

harmonization, and not at all a stubborn ignorance of the other side

or a compromise with cheap concessions, was the aim of the period from

Kant to Emerson. It is merely the naturalistic period which ignores its

idealistic counterpart, which delights in its one-sidedness, which is

afraid of harmony because it is suspicious of demands for concessions.

It is naturalism only which thinks that mankind can walk on one leg.

If we ask where such harmonization can be found, where the great

Idealists of the beginning of the last century have sought it, and

where our modern philosophy is seeking it again, well aware that by

the progress of science in the mean time the difficulties have been

multiplied, the logical responsibilities have become gigantic, we

cannot do more here than to point out the direction; we cannot go

the way. And it is clear, of course, too, that such an answer has its

individual shape, and that no one can promise to give a bird's-eye

view of the marching movement while he is himself marching among his

comrades. But the individual differences are non-essential. The one

great tendency, the Emersonian spirit, if it is rightly understood,

is common to them all. What has modern philosophy all over the world

to say about that threefold claim concerning Nature, Freedom, and

Oversoul? What has it to say when natural science has fully said its

say and had its fair hearing, and has been approved as sound and

welcome?

A philosopher might answer, perhaps, as follows: You Positivists have

done wonderfully with your microscopes and your telescopes, with your

chronoscopes and spectroscopes; you have measured and weighed and

analyzed and described, and finally explained the whole world which you

perceive, and there is nothing in space and time and causality which

can escape your search. But did not all that work of yours involve

certain presuppositions which you had accepted and which it was not

your business to look on critically, but which, nevertheless, may be

open to enquiry? Your first claims granted, all may follow; but how is

it with the first claims? You examine all that is in space and time,

but what are space and time? You examine the material substances and

the contents of consciousness, but what is consciousness, and what is

matter? You seek the special applications of causality, but what is

causality? Well, you reply, you give the facts just as you find them;

but do you do that really? And what do you mean by saying that you find

the facts? Let us look, at least for a moment, at the very simplest

facts with which your work begins. You say there are physical objects

made up of atoms, and you describe them as a physicist; and there are

mental ideas in consciousness made up of sensations, and you describe

them as a psychologist; and both, you say, you are finding. But what

does it mean, that you find the physical object outside there and the

mental idea of the object inside in you; is that really a statement

of your immediate experience? The physicist speaks of this table here

before me, outside of me; and the psychologist speaks of my idea of

this table, enclosed in my consciousness. Both may do well to speak

so; but will you make me believe that I find that doubleness in my

experience? If I see this table and want to use it, I am not aware

of one table of wooden stuff and another in me of mental stuff. I am

not aware of a two-ness at all, and if the physicist says that this

wooden table is made up of molecules and has in itself no color and

no continuity, and that the mental idea in me furnishes all those

qualities of color and smoothness, but has no solidity, then they

speak of two interesting worlds about which I am anxious to know, but

certainly neither of them is the world I live in. If I lean on this

table I am not aware of a table in my mind at all. I know the one table

only, and this one table has its color and its smoothness.

I know what you will answer. You will say, in your immediate experience

there are indeed not two worlds of objects, a physical and a

psychical; the real thing to which our interests in life refer is not

differentiated into a molecular object outside of us and a sensational

object in us, but it is clear that every real thing allows a kind of

double aspect; we can consider this table in so far as it is common to

all of us, in so far as it is a possible object for every one of us,

and in so far as it becomes an object for the individual, and we can

then call the objects, in so far as they are common property, physical;

and in so far as we take the aspect of individual relations, psychical;

and as it must be of the highest importance for our practical purposes

to discriminate between those two aspects, we have clearly the right

to consider the world from the point of view of both the physicist

and the psychologist. It is, of course, an abstraction if we leave

out in the one case the one side, in the other case the other side

of our objective experience; but we gain by that the possibility of

constructing two closed causal systems of which each one must have its

special conditions of existence, inasmuch as the one is conceived as

related to individuals and the other as independent of individuals.

Very true, we should answer. Something like that saves you completely,

justifies fully your claim to separate the physical and the psychical

worlds of objects, the world of matter and the world of ideas; but

can you deny that you have lost your case, are you not now yourself

in the midst of philosophical, methodological discussions, which your

physics and psychology themselves cannot settle, yet which must be

settled before they can enter into their rights; and above all, do you

not yourself see now that your whole physics, for instance, is not at

all an account of reality, but merely a certain logical transformation

of reality; that you do not find the world of physics at all, just as

little as you find the psychical ideas, but that you can merely work

over and reshape the reality which you find till you construct out

of it your world of matter and your world of consciousness? What you

believed you would find you have never found, while your construction

of physical things may have been most necessary for your purposes; but

do not deny that you have left reality far behind you.

And so it is with all your doings. You tell us proudly, for instance,

that you show us the deepest nature of the world by showing us the

elements which the object contains, and that you thus bring us at least

nearer to the essence of things; and yet if we begin to look into your

real achievements, we are disappointed again to find that you are far

away from even attempting anything of the kind. You tell us that water

is hydrogen and oxygen, and if we say "Prove it," you show us simply

that you can transform the water into hydrogen and oxygen, and that

you can transform these two elements again into water. Is that really

what you promise? We want to know what the thing is, and you show us

simply how the one thing can be transformed into another thing; and

whenever we turn to your wisdom, it is always the same story. You show

us always, and most nicely, how the one goes over into the other, but

you never show us what the one or the other really is in itself. For

your practical purposes the first may be the most important aspect,

but do not make us believe, therefore, that it is the only possible

aspect. In short, whether science describes or explains, it never

gives us what we find in reality, but makes out of reality a new ideal

construction in the service of certain purposes, and never gives us

the things as they are, but merely the effects and changes which they

produce. Are we still, then, to be deeply impressed with the claim

of the naturalist that he alone has the monopoly of knowing reality,

while we see now that every step of his leads us away from reality? And

have we still to be afraid to raise the voice as philosophers with the

claim that reality itself must find its expression, that there must be

a science which shall give account of reality as we really find it,

of nature before it is made up and repolished for the purposes of the

physicist? Only if we have such other account of nature, then only

do we speak of that nature in which we live and in which we act, and

compared with such an account of the fuller reality, the constructed

schematism of the physicist must appear, indeed, as Emerson said,

"barren like a single sex." Not the slightest result of natural science

is depreciated, not the slightest discovery ignored, if we insist that

all these so-called facts have a meaning only under certain artificial

conditions which set them apart from the reality of our life; and in

this reality lies the interest of the philosopher. We have thus no

reason to reproach the scientist so long as the scientist does not

fancy that his science gives an account of nature as it really is. Both

kinds of work are necessary, and the scientist may well speak, as the

squirrel in Emerson's poem:

"Talents differ,

All is well and wisely put;

If I cannot carry forests on my back,

Neither can you crack a nut."

Natural science has to crack our nuts, but philosophy has to carry

on its back the flourishing forests of life, in which we wander and

breathe. And if Emerson is right, to-day and forever, in claiming that

the facts of natural science are not expressions of reality, it is only

a small step to see that he was not less right in saying that man is

free. Consider man as a particle in the physical universe, consider his

actions from the point of view of a causal science, and there is no

possibility of escaping materialism and fatalism. We must understand

every activity as a necessary outcome of foregoing conditions.

Psychology must do so, and physics must do the same. The empirical

sciences would be disloyal to their own principles if they allowed

the slightest exception. The noblest gesture, the greatest word, the

bravest action, must be considered by them under the category of

causality. They are necessary effects of all the preceding causes. It

may be interesting, it may be fascinating to follow such lines with the

enthusiastic energy of scholarly research. But are we really obliged

to accept the outcome as an ultimate word concerning the meaning of

our freedom? "Forever wells up the impulse of choosing and acting in

the soul." Is it really merely an illusion? Has responsibility still

its moral value, are we the actors of our actions, are we still good,

are we still guilty, when every deed follows as necessary effect? Is

not, then, the whole constitution of the world, which has made us,

responsible whenever we move our hand for good or for bad?

But we know now where we are standing; we know now that the world

of objects, of psychical as well as of physical, is a constructed

world, constructed for the purpose of satisfying our demand for causal

connection; for that world holds causality because it is the world

seen from the point of view of causality; and just as there cannot be

anything in that world of physical and psychical objects which is not

causally connected, just so it cannot have any meaning at all to ask

for causal connection before the world is conceived in the service of

this artificial construction. Reality in itself is not causal, and to

ask for the causes of the real experience of our inner life has not

more meaning than to ask how many pounds is the weight of a virtue, and

how many inches is the length of our hopes. But we must go farther.

To apply the question of cause and effect to our real will means not

only that we apply to the real object a standard which belongs to

the artificial or constructed object, but it means above all that we

consider as an object something which in reality is not an object at

all. The will which the psychologist describes and must describe, the

will which has causes and which is thus not free, is a will conceived

as an object found in our mind like an idea, something of which we are

aware, something whose happening we perceive, and yet if anything is

sure it is the immediate experience that we are aware of our will in

a way which is absolutely different from the way in which we perceive

objects. We do not perceive our will at all, we will it, we strive

it, we fight it; yes, we feel ourselves, only in so far as we are the

subjects of will. Our will is our personality, which we do not find but

which we are, and which stands opposed and separated by the deepest

gulf from the world of objects. Those objects are means and purposes of

our will, are ends and aims and instruments; but they come in question

for us only as we will them, as we like and dislike them, as we approve

and reject them. And if we take this world of objects and reconstruct

it into the artificial world of physical and psychical things connected

by causality, in this very act of reconstruction we feel ourselves as

willing, deciding, approving, aiming personalities, whose wills decide,

who think the world as causally connected, whose freedom guarantees

the value of our conception of a world not free. There is no knowledge

but in our judgments; there is no judgment but in our affirming and

denying; there is no affirming and denying but in our will. Our will

chooses for its purposes to conceive reality as if it were unfree.

What a climax of confusion to think that this conception of an unfree

world, the conception of science, can itself now condemn the freedom

of the will which has chosen. "Freedom is necessary," said Emerson. We

can add, necessity itself is merely a purpose determined by freedom.

"Intellect annuls fate," Emerson says. We may add, fate is merely an

idea of intellect. Let us be psychologists if we want to analyze, to

calculate, to explain the unfree man; but let us be philosophers to

understand what it means to be a psychologist. Now the synthesis is

reached; the real world is free, but we choose for our purposes to

conceive the world as unfree, and thus to construct causal sciences.

And if we understand that in reality man is free and that the

psychological aspect of man as unfree is a special way of looking on

man for special purposes, then suddenly there opens itself before

us the vast field of history, and the historical life, which seemed

deprived of all interest by the psychological, iconoclastic mood,

suddenly wins again a new importance. We feel instinctively that

this free man of reality, this man who is a responsible actor of his

actions, he only is the agent of history; and history is falsified

and cheapened when it is brought down to a causal explanation of

psychological man instead of real man. History had become an appendix

of sociology, and what great historians aimed at in the interpretation

of the few "stout and earnest personalities" seemed lost in favor of a

construction in which the great man and the genius rank with the fool

as mere extreme variations of psychological averages. Now suddenly do

we understand that history has to deal with the world of freedom, that

it has not to explain, but to interpret, that it has not to connect

the facts by linking causes and effects, but by understanding the

meaning of purposes, their agreement and disagreement, their growth

and liberty. Now we understand why Fichte, why Carlyle, why Emerson

believes in heroes and hero-worship, why Idealism has been at all

times the fertile ground for writing history and for making history,

while Naturalism has made technique, and thought in an anti-historical

spirit. Our time begins again to think historically. It can do so

because it again begins to emancipate itself from its positivistic

disbelief in man's freedom and from its unphilosophic superstition that

causal science alone is science, that we know only when we explain.

And when we at last stand man to man in full freedom, no longer as

psycho-physical constructions but as free personalities, and when we

debate and try to convince each other, will you deny that Jove stands

behind each of us and Jove nods to Jove when we meet? Would it even

have a meaning for us to go on with our talk, should we try at all

to convince each other if you thought and I thought, each one for

himself, that our will is only our personal will, that there is no

over-individual will, no Oversoul behind us? Can we discuss at all if

we do not presuppose that there is really a truth which we are seeking

in common, that there are certain judgments which we are bound to will,

which we are obliged to affirm, which we will, but not as individuals,

and of which we take for granted that every one whom we acknowledge

at all as a personality must will them too; and if you come with the

flippant air of the sceptic and tell me, "No, there is no truth, all

is only as it appears to me, there is no objective truth," do you not

contradict yourself, are you not saying that at least this, your own

statement, expresses objective truth; that you will this with a faith

and belief that this will of yours is an over-individual will which

is, as such, a duty, an obligation for every one who thinks? Every

escape is futile. And all the over-individuality that lives in our

will towards truth comes to us again in our will towards morality. Do

not say sceptically that there is no absolute obligation, that you do

not feel bound by an over-individual will in your action, that you

will do in every moment what pleases you individually. You cannot even

speak this sceptical word without contradicting yourself again, as you

demand through the fact of your saying it that we believe that you

speak the truth and that you thus feel yourself bound not to lie. If

you leave us doubtful whether your word was not a lie, the word itself

cannot have any meaning. Do not try to dodge the Oversoul. Men live

and fight in its purposes, and men descend to meet. It is as Emerson

said, "At first delighted with the triumph of the intellect, we are

like hunters on the scent and soldiers who rush to battle; but when the

game is run down, when the enemy lies cold in his blood at our feet,

we are alarmed at our solitude." Let the sociologists triumphantly

reduce the ideals to necessary social products of evolution in the

same spirit in which the psychologist eliminates the freedom of the

individual; but let us never forget that such a social mechanism is as

much an artificial construction necessary for its purposes as is the

psycho-physical mechanism of individuality. In that reality with which

history deals, in which our freedom lies, there our over-individual

will comes from deeper ground than from the soil and the food and the

climate. Our logical obligations, our ethical duties, our æsthetic

appreciations, our religious revelations, in reality they do not come

from without, they come from within; but from within as far as we are

souls in the Oversoul. There is no duty in the world but the duty

which we will ourselves; no outer force, no training, no custom, no

punishment can make us have duties. Duty is our will, it may be the

duty to think for the ideal of truth, the duty to feel for the ideal

of æsthetics, the duty to act for the idea of morality, the duty to

have faith in the ideal of religion; but it is always our own will,

and yet not our fanciful, personal, individual will. It is a system

of purposes upon whose reality all knowledge of the world, and thus

the world as we know it, is dependent forever. The wave of Idealism

is rising. The short-sighted superstition of Positivism will not lurk

under the roof of a new hall of philosophy. To be a true student of

the most scientific, of the most scholarly, of the most insistent

philosophy means to respect and to study the sciences, the physical and

the psychical sciences, but at the same time to understand that natural

science is not the science of reality, that psychology does not touch

the freedom of man, that no life has a meaning without the relation to

the Oversoul. We cannot write a whole system and a whole text-book

on the front of the new building. It must be enough to write there a

symbolic word; happy, forever happy, the university which can write

over the door of its temple of philosophy the name: Ralph Waldo Emerson.

IV. THE PLACE OF EXPERIMENTAL PSYCHOLOGY

[At the opening of Emerson Hall, December 27, 1905, the American

Psychological Association discussed the relation of psychology to

philosophy; I opened the discussion with the following remarks:]

From the whole set of problems which cluster about psychology and its

relation to neighboring sciences, this hour, in which Emerson Hall is

completed, and this room, in which I hope to teach psychology to the

end of my life, suggest to me most forcibly to-day the one question:

Have I been right in housing psychology under this roof? I might have

gone to the avenue yonder and might have begged for a psychological

laboratory in the spacious quarters of the Agassiz Museum, to live

there in peaceful company with the biologists; or I might have

persuaded our benefactors to build for me a new wing of the physical

laboratory. But I insisted that the experimental psychologists feel at

home only where logic and ethics, metaphysics and epistemology keep

house on the next floor.

I certainly do not mean that the psychologist ought to mix the records

of his instruments with the demands of his speculations, and that he

may seek help from the Absolute when the figures of the chronoscope

or the curves of the kymograph are doubtful. Experimental psychology

is certainly to-day and will be for all future an independent exact

discipline with its own problems and methods. No one can insist more

earnestly than I do on the demarcation line between the empirical study

of mental phenomena and the logical enquiry into the values of life.

Yet I deny that it is a personal idiosyncrasy of mine to try to combine

vivid interest in both. There is no antagonism between them; a man may

love both his mother and his bride. I am devoted to philosophy, just

as I love my native country; and I am devoted to psychology, just as I

love the country in which I do my daily work; I feel sure there is no

reason for any friction between them.

Of course, on the surface a psychological laboratory has much more

likeness to the workshop of the physicist. But that has to do with

externalities only. The psychologist and the physicist alike use subtle

instruments, need dark rooms and sound-proof rooms, and are spun

into a web of electric wires. And yet the physicist has never done

anything else than to measure his objects, while I feel sure that no

psychologist has ever measured a psychical state. Psychical states are

not quantities, and every so-called measurement thereof refers merely

to their physical accompaniments and conditions. The world of mental

phenomena is a world of qualities, in which one is never a multiple of

the other, and the deepest tendencies of physics and psychology are

thus utterly divergent.

The complicated apparatus is therefore not an essential for

the psychologist. Of course, we shall use every corner of our

twenty-four laboratory-rooms upstairs, and every instrument in the

new cases--and yet much of our most interesting work is done without

any paraphernalia. Three of the doctor-dissertations which our

psychological laboratory completed last year consisted of original

research in which no instruments were involved; they dealt with

memory-images, with associations, with æsthetic feeling, and so

on. Yes, when, a short time ago, a Western university asked me how

much it would cost to introduce a good practical training-course in

experimental psychology, I replied that it would cost them the salary

of a really good psychologist, and besides, perhaps, one dollar for

cardboard, strings, rulers, colored paper, wire, and similar fancy

articles at five cents apiece.

On the other hand, I do not know a psychological experiment which

does not need a philosophical background to bring its results into

sharp relief. Of course, you will say, the psychologist deals with

facts, not with theories, and has to analyze and to describe and to

explain those facts. Certainly he has to do all that; only he must

not forget that the so-called "fact" in psychology is the product of

complex transformations of reality. A will, an emotion, a memory-image,

a feeling, an act of attention, of judgment, of decision--these are

not found in the way in which stones and stars are noticed. Even if

I choose perceptions or sensations as material for my psychological

study, and still more when I call them _my_ perceptions and _my_

sensations, I mean something which I have found at the end of a long

logical road, not at its starting-point, and that road certainly leads

through philosophy. Emerson said wisely, "A philosopher must be more

than a philosopher;" we can add: A psychologist must be more than a

psychologist. First of all, he must be a philosopher.

What would be the result if our laboratory had moved to the

naturalistic headquarters? It would be the beginning of a complete

separation from philosophy. Our graduate students would flock to

psychological research work without even being aware that without

philosophical training they are mere dilettantes. And soon enough a

merely psychological doctorate would be demanded. I do not deny at

all that such pure psychologists would find enough to do; I should

doubt only whether they know what they are doing. There are too many

psychologists already who go their way so undisturbed only because they

walk like somnambulists on the edge of the roof; they do not even see

the real problem; they do not see the depths to which they may fall.

But does the laboratory itself gain from such divorce? Just the

contrary. It is evident that everywhere in the world where the

psychological laboratory turns to natural science, the experiments

deal mostly with sensation, perception, and reaction; while those

laboratories which keep their friendship with epistemology emphasize

the higher mental functions, experimenting on attention, memory,

association, feeling, emotion, thought, and so on. But is it not clear

that only the latter work gives to the psychological laboratory a real

right to existence, as the former is almost completely overlapped by

the well-established interests of the physiologists? If psychology

cannot do anything else than that which physiologists like Helmholtz,

Hering, Kries, Mach, Bowditch, and the rest have always done so

successfully, then experimental psychology had better give up the trade

and leave the study of the mind to the students of the organism.

I have said that we ought not to depend on authorities here. Yet

one name, I think, ought to be mentioned gratefully in this hour in

which the new psychological laboratory is opened for work. I think

of Professor Wundt of Leipzig. The directors of the psychological

laboratories in Columbia, and Yale, in Clark and Chicago, in

Pennsylvania and Cornell, in Johns Hopkins and Washington, in Leland

Stanford and Harvard, and many more are his pupils. Some weeks ago,

when I did not foresee our present discussion, I told him of Emerson

Hall; and a few days ago I got an answer from which, as my closing

word, I may quote in translation. Professor Wundt writes to me: "I am

especially glad that you affiliated your new psychological laboratory

to philosophy, and that you did not migrate to the naturalists.

There seems to be here and there a tendency to such migration, yet I

believe that psychology not only now, but for all time, belongs to

philosophy: only then can psychology keep its necessary independence."

Mr. Chairman, these are the words of the father of experimental

psychology. I hope they indicate the policy to which Harvard University

will adhere forever.

V. THE PSYCHOLOGICAL LABORATORY IN EMERSON HALL

A monumental staircase leads from the first--the lecture-room--floor

of Emerson Hall to the second, the library floor; at the two ends of

its broad corridor smaller staircases lead to the third floor, the

laboratory. Its general division of space is seen at a glance from the

sketch of the ground plan (opposite page 1). Eighteen rooms of various

sizes with outside windows form a circle around the central hall

which is well lighted by large skylights; but at each end of the hall

itself two large windowless spaces are cut off and each of these is

divided into three dark rooms. We have thus twenty-four rooms, besides

coat-room, toilet-rooms, etc. A further stair leads to the wide attic

which is mainly a store-room for the institution.

In order that the laboratory should be adaptable to the most diverse

purposes, the permanent differentiation of the rooms has been kept in

narrow limits. It seemed unwise to give from the first every room to a

special line of research, as the preponderance of special interests may

frequently shift; there are years when perhaps studies in physiological

and comparative psychology make the largest demand and others in

which studies in æsthetical and educational psychology stand in the

foreground. A thorough-going specialization, by which special rooms

are reserved for tactual studies and others for chronoscope work or

for kymograph researches, allows of course certain conveniences in the

fixed arrangement of instruments and a certain elaboration of equipment

that is built in, but it very much impairs the flexibility of the

whole laboratory, and has thus not seemed advisable for an institution

whose catholic attitude welcomes investigations as different as those

contained in this volume.

To be sure certain constant requirements have demanded a special

fitting up of one room as a workshop, one room for the more

delicate instruments, one for the beginning course in experimental

work, a lecture-room for the courses in comparative psychology, a

photography-room, a battery-room, a sound-proof room, the chief animal

rooms, and the dark rooms. We have seven light-proof rooms, finished

in black, of which two have outside windows for heliostats; of the

others, four can be used for optical research; the longest one contains

the photometer. Six other rooms, including the lecture-room, may be

darkened by opaque blinds. One contains a partition with door and a

grooved window-frame fitted with screens in which openings of any

desired size and shape may be cut. This window is opposite the main

door of the room, and opposite this, across the central hall, some

sixty feet away, is the door of another dark room; optical stimuli can

thus be given from this window to a subject over seventy feet away.

Several rooms are fitted up with special reference to the investigation

of the various forms of organic movement, animal behavior and

intelligence. As one result of several investigations in animal

psychology already pursued here, the laboratory has a considerable

number of devices for testing and making statistical studies of the

senses and intelligence, methods of learning and emotional reactions of

animals.

Adequate provision is made for the keeping of animals in a large,

well-lighted, and well-ventilated corner room. Instead of having

aquaria built into the room, an aquarium-table eighteen feet long has

been constructed to support moveable aquaria of various sizes. Whenever

it is desirable for the purposes of an investigation, any of these

aquaria may be moved to the research-room of the investigator or to

such quarters as the special conditions of the experiment demand.

The vivarium-room contains, in addition to provisions for

water-inhabiting animals, cages of a variety of forms and sizes. The

largest of these cages, six and a half feet high, six feet wide,

and four feet deep, may be used for birds, monkeys, or any of the

medium-sized mammals. Cages for rabbits, guinea-pigs, and other small

animals are arranged in frames which support four double compartments.

Similarly, small cages suitable for mice, rats, and other small rodents

are in supporting frames which carry four of the double cages, each of

which is removeable and may be carried to the experimenting-room at the

convenience of the experimenter.

In a large unheated room above the main laboratory are tanks for

amphibians and reptiles. These tanks, since they can be kept at a low

temperature during the winter, are very convenient and useful for

frogs, tortoises, and similar hibernating animals.

In view of the prime importance of electricity to a modern

psychological laboratory, a rather elaborate system of wiring has

been designed and built in. The unit of this system is a small

delivery-board six inches wide by eight inches high, which carries

the following five circuits: _a_, a time-circuit for running magnetic

signals; _bb_, two low-tension circuits for chronoscope, bells,

signals, etc.; _c_, a high-tension alternating current (110 v. and 60

phases) for alt. current motors, to be used where great constancy of

speed is desired; _d_, a high-tension direct current (110 v.) for dir.

current motors, where it is desired to vary the speed continuously (by

the introduction of resistance). Two such delivery-boards have been

set on opposite walls of all except the smallest rooms, which have

but one board. Circuits _a_ and _b_ are represented on the board by

binding-posts, while the high-tension currents, _c_ and _d_, appear as

flush, protected sockets that take a double-pole plug.

Circuit _a_ is a single circuit led from a time-pendulum permanently

set in the battery-room, and carried once around the laboratory. It is

connected with the _a_ binding-posts of the individual delivery-boards

in parallel. It follows that the time-circuit is alike for all the

rooms at any one time; but in different hours the pendulum can be

adjusted to give various impulse-rates. If an investigation requires

some special rate of impulse, the special time-apparatus is set up in

the investigator's room and current for it taken from one of the _b_

pairs of posts.

Each _b_ pair goes directly from the delivery-board to the battery-room

and ends at a double-pole (telephone type) socket on a large

switch-board. Thus every room has two or four direct and independent

connections with the battery-room.

The _c_ and _d_ circuits do not come from the battery-room, but from

their respective generators that are stationed outside of the building.

They are of course connected at the delivery-boards in parallel.

The large switch-board in the battery-room consists of an upper and a

lower part. The upper part bears the double-pole sockets from the _b_

posts in all the rooms; the lower part carries some fifty pairs of

single-pole sockets that are connected with the batteries stationed

near by. These pairs are labelled, and some give a current from cells

of the Leclanché type, others of a gravity type. The student has merely

to choose the kind and number of cells that he needs, from the lower

part, and connect them with one of the double-pole sockets of the

upper part which runs to a _b_ pair in his own room. By connecting

two double-pole sockets with each other, the student can establish a

circuit between any two rooms of the laboratory,--this for purposes of

telephonic or other communication. Since every room has two, and most

of the rooms have four of the _b_ circuits, the greatest variety and

elasticity of service is attained.

The large switch-board further carries a voltmetre and an ammetre,

both of the Weston make, which are reached (electrically) from

double-pole jacks (sockets) on the upper part of the board. Thus

before connecting the current with his room, the student can in a

moment measure its amount and intensity. These instruments are of the

flushface type, and dead-beat.

All of the rooms are lighted by electricity, and the lighting system

is independent of the delivery-boards. Nine of the rooms are provided

with soapstone sinks, and six (not including the lavatories and

service-room) with enamelled iron or porcelain sinks. All the sinks

have two taps and each of these ends with a screw-thread so as to take

a tip and rubber hose. The soapstone sinks were specially designed

with soapstone drip-boards. This is probably the best material for a

research-room, and the porcelain and enamel sinks were put only where a

neater appearance was desired, or where chemicals were to be frequently

used--as for instance in the battery and photographic rooms. Gas is not

used for illumination, but six rooms are provided with jets for the

smoking of drums, soldering, brazing, etc.

The instrument-room is equipped with large dust-proof cases for holding

the more delicate and valuable instruments. The larger unused pieces

are stored, out of sight but readily accessible, in an attic which has

a clear floor-space of something more than half the total area of the

laboratory. Dust-proof cases for demonstration and class-work material

are provided in the lecture- and class-rooms.

The shop contains a wood-working bench with two vices, tool-racks,

shelves, drawers, cupboards, and stock-racks, for the use of students;

and a 9-in. lathe, circular saw, grinding- and buffing-machine,

separate bench, vice, racks, and drawers for the use of the mechanic.

The machinery is run by a 5 h.p. electric motor suspended from one of

the outside brick walls, on brackets. One who selects the equipment of

such a shop has to weigh carefully the respective merits of circular

and band saws; the latter undoubtedly lends itself to a greater variety

of uses, but it is also a far more dangerous machine to have running

in a room to which students are to be given access. This latter

consideration determined in the present case the choice of a circular

saw. It is quite dangerous enough, and may be used only by, or under

the supervision of, the mechanic.

It has been stated on competent authority that a truly sound-proof

room cannot be built except under ground. This has not been

attempted, but the laboratory contains one room (no. 17) which is

virtually sound-proof. A double door separates it from the adjoining

experimenter's room, and double doors also separate this from the

main hall. The wall between these two rooms consists of two layers of

plaster with special deadening material inserted between. Two small

tubes, ordinarily stuffed with felt, connect these rooms. When the

acoustical stimulus is a tuning-fork, it is placed in a distant room,

connected with one of the _b_ circuits of the sound-proof room, and

then with a telephone receiver near the subject's ear.

The photographic-room contains the ordinary sink, red lights, shelves,

etc. The indirect entrance is light-tight when the door is not closed,

so that the experimenter may pass in and out even when developing is

going on. This room, like all the others which have no window (except

the sound-proof room), has forced ventilation.

The class-room is designed for the experimental training-courses. It

has eight of the regular delivery-boards, ten tables, instrument-case,

blackboard, and sink.

The lecture-room for specialized courses in comparative and

experimental psychology seats eighty students. It is provided with

two Bausch and Lomb electric projection-lanterns, horizontal and

vertical microscope attachments, and attachment for the projection of

opaque objects. On the lecturer's platform, besides the blackboard,

projection-screen, and chart-racks (capable of holding twenty charts),

is a large demonstration-table provided with a delivery-board, water,

gas, sixteen chart-drawers, two other drawers, and three cupboards.

As has been said before, the general psychology course of the

University is not given on the laboratory floor, but downstairs

in the large lecture-hall with about 400 seats. A number of large

demonstration instruments of the laboratory serve the special purpose

of this course; this hall too has its own stereopticons.

Our instrumentarium is, of course, in first line, the collection of

apparatus bought and constructed through the fourteen years of work.

Yet with the new expansion of the institute a considerable number of

psychological, physical, and physiological well-tested instruments has

been added. Especially in the departments of kymographic, chronoscopic,

and optical apparatus the equipment presents a satisfactory

completeness; its total value may be estimated to represent about

twelve thousand dollars. Yet the place of the laboratory which we

appreciate most highly is not the instrument-room but the workshop,

in which every new experimental idea can find at once its technical

shape and form. Whether those experimental ideas will be original and

productive, whether their elaboration will be helpful for the progress

of our young science, in short, whether the work in the new laboratory

will fulfil the hopes with which we entered it, may be better decided

as soon as a few further volumes of the Harvard Psychological Studies

shall have followed the present one, which is still from cover to cover

a product of Harvard's pre-Emerson-Hall period.

OPTICAL STUDIES

STEREOSCOPIC VISION AND THE DIFFERENCE OF RETINAL IMAGES

BY G. V. HAMILTON

The question which the Laboratory proposed to me for experimental

enquiry was one which demanded a definite reply of yes or no. The

positive answer seemed a necessary consequence of the traditional

psycho-physiological theories, while a certain practical consideration

seemed to suggest the negative solution. The question which seems

to have been overlooked so far was this: According to the theory of

stereoscopic vision two points of light which are seen by each of the

two eyes under the same angle appear to lie in the same plane; as soon

as the angle for the right eye is larger than that for the left, that

is, as soon as the two stimulated retinal points in the right eye are

more distant than the two retinal points stimulated in the left eye,

the right light-point seems to be farther away than the left one. If we

relate them to planes vertical on the ideal binocular fixation-line,

the right point lies in a more distant plane. This principle, which, of

course, controls all arrangements for stereoscopic effect, is deduced

from experiences in which the fixation-line is vertical to the line

that connects the nodal points of the two eyes; the plane in which

the equally distant points lie is then parallel to the forehead. If,

on the other hand, the eyes are turned to the side, that is, if the

ideal fixation-line forms an acute angle with the line connecting

the eyeballs, the two fixated light-points, which lie in a plane

perpendicular to the fixation-line, cannot be seen by the two eyes

under the same angle. Any object on my right side is somewhat nearer

to my right eye than to my left, and therefore must throw a larger

image on my right retina. The two light-points of a plane vertical

to the fixation-line give thus with the eyes turned to the right two

unequal pairs of retinal stimuli; and the difference of the retinal

stimulations is evidently just the same as if the eyes were looking

straight forward but the two lights were at different distances. If

difference of retinal images really produces the conscious experience

of seeing the lights in differently distant planes, vertical to the

fixation-line, it follows that with the eyes turned to the right,

lights which objectively lie in the same plane must appear subjectively

to lie in different distances. The question arises whether the facts

correspond to this conclusion. If we look with eyes turned sidewise

towards a plane vertical to the direction of seeing, do the points

of that plane remain in it for consciousness or do we see them in

different planes? We see that practical considerations suggest a "No"

to this question, because it would mean that everything which does

not lie exactly in front of us must change its plastic form, and

this the more strongly the more we see it on our right or our left,

and this of course again the more strongly the nearer it is to the

eyes, inasmuch as the relative difference of the retinal images must

increase with the nearness of the object. If a short-sighted person

fixates an object a few centimetres from the eyes strongly turned to

the side, the distances in the retinal image of the one eye may be

almost the double of those in the other. Under normal conditions the

differences would be smaller, but yet everything would be necessarily

distorted in its three-dimension shape as soon as it is seen in

indirect vision or with sidewise fixation. On the other hand, if the

objects keep their three-dimensional relations in spite of sidewise

movements, it is evident that the accepted psycho-physiological theory

of stereoscopic vision is incomplete and must be revised in a very

essential way. The experiment had to decide. Of course the question

might be approached experimentally in different ways. It would have

been possible, for instance, to study the stereoscopic synthesis of two

separate flat pictures seen with the eyeballs in different positions.

But we preferred the simplest possible way, seeking the threshold of

distance for two parallel vertical edges with eyes turned forward and

to the side. We chose edges instead of hanging threads for the purpose

of avoiding the possible influence of the apparent thickness of the

threads on the judgment of distance. Of course, distance is here never

distance from the one or the other eye, but from the centre of the

line which connects the two nodal points of the eyes; the two vertical

planes whose edges were to be compared stood always vertical on the

ideal line of fixation which starts from that central point between the

two eyeballs.

The apparatus used in these experiments consists of three parts, viz.:

(1) A plank 2.5 metres x 9.5 centimetres x 4 centimetres, set on edge

and screwed to a table at either end.

(2) A head-rest 45 centimetres high, 35 centimetres broad and 15

centimetres deep. Attached to the centre of the lower strip of the

frame is a concave trough for the chin. Another trough, shaped to

fit over the vertex and with a strip of wood fastened to the front

of it for the forehead, slides up or down within the frame. The

attachment for the forehead can be moved and fixed at various positions

antero-posteriorly. By means of these devices the head can be securely

fixed in any position desired without discomfort to the subject.

In order to have the eyes always in the same plane and at a known

distance from the apparatus at the other end of the plank, a hole was

made in either side of the frame with its centre at a level of the

eyes. Extending through the vertical diameter of each hole is a fine

wire. Fitted into the inner portion of each hole is a cardboard tube 10

centimetres long: the inner end of each tube contains a vertical wire

so arranged that the four wires all fall into a plane at right angles

to the long direction of the plank. A mirror at the outer exit of

either hole enables the experimenter to align the tips of the subject's

corneæ with the wires.

Two parallel strips of wood are so attached to the "head-rest" end of

the plank--one below and the other above it--that they can be rotated

laterally upon the plank, with the bolt which secures them to it for a

centre of rotation. Opposite this centre, and attached to the anterior

surface of the upper parallel strip is a wire needle 25 centimetres

long. By means of a quadricircular piece of cardboard attached to the

plank at the end of the needle, the extent of rotation to the right

or left can be read off in degrees. (The point midway between the two

corneal tips when they are aligned with the wires is in the same axis

of rotation as the head-rest.)

A vertical iron rod 50 centimetres long extends upwards from either end

of the parallel strips, and upon these rods the frame of the head-rest

can be moved up or down by means of thumb-screws upon which it rests.

(3) At the opposite end of the plank there is attached a flat board,

35 centimetres long and 30 centimetres wide. Attached to the edge of

the board which faces the head-rest is a piece of black cardboard

40 centimetres long by 35 centimetres broad. In the centre of the

cardboard is a rectangular aperture, 7 centimetres by 14 centimetres.

On the upper surface of the board are two slots, one at either side.

Sliding within each of these slots is a block of wood to which is

attached an upright sheet of black-painted tin, 15 centimetres wide and

20 centimetres high. The surfaces of these tins lie in planes parallel

to the plane of the four wires in the head-rest, when the latter is

at right angles to the plank. When their surfaces are equidistant

from the wires, the inner vertical edges of the tins are separated

from each other by 3 centimetres. The sides of the slots, in which

the blocks with their tins slide, are fitted with millimetre scales,

thus enabling the experimenter to determine the distance of the edges

from the corneæ. The point on the scale at which an edge was exactly 2

metres from the vertical plane of the wires was chosen as the "zero"

point, and if this distance was decreased by moving an edge forward,

the latter was said to stand at "minus" one, two, or more millimetres,

as the case might be. Likewise, an edge was said to stand at "plus"

the number of millimetres' distance beyond the zero point if it had

been moved at a greater distance than 2 metres from the wires. A piece

of ground glass attached to the distal end of apparatus enabled the

experimenter to secure a uniform illumination, the room being darkened

and the light coming from a 32-candle-power electric lamp set about a

metre and a half behind and on a slightly lower level than the glass.

It was found that by shading the lamp itself and admitting a dim

light to the room by means of drawing down only the ordinary thin

window-shades, the edges could be made to seem almost isolated in space

and to stand out in clear relief.

The subjects of the experiment were Messrs. Bell, Flexner, and Tait.

Each subject determined the equality-point and the threshold for the

normal primary position of the eyes, for the eyes in a lateral position

of 15° and in a lateral position of 30°, both to the left and to the

right.

Eyes at 0° means the following: that the most anterior part of the two

corneæ lies in a plane parallel to and two metres' distance from the

plane in which the two parallel edges lie at 0. Eyes at 30° to the left

means that a line drawn in front of the two corneæ intersects such a

line at an angle of 30°, the left eye being at the distal end of the

line. In calculating the visual angles 7.4 mm. are added in order to

compensate for the distance from the extreme anterior portion of the

cornea to the nodal point of the eye.

The results for Mr. Tait are as follows:

The position of eyes 0°. The right edge was moved, at first from an

evident + position to equality, then from equality to the - threshold,

then from an evident - position to equality, then from equality to

the + threshold. These four points were determined each fifteen times

and the average taken. Then exactly the same fifteen sets of four

determinations with the left edge moved. The averages of these 120

experiments are these: When the left edge is moved from + to =:-2.77,

from = to -:-6.97, from - to =:+0.77, from = to +5.93. When the right

edge is moved from + to =: +2.83, from = to -:-1.6, from - to =:+5.9,

from = to +:+10.53. The first equality-point appears thus when the left

edge is moved at -0.76, when the right edge is moved at +4.41, with a

threshold of about 5 in either case. With the normal eye-position the

edges must thus not be exactly in the same plane to appear equally

distant; at a distance of 2000 mm. the left must be about 2 mm. nearer

than the right to appear in the same plane, vertical to the line of

regard.

If the position of the eyes is 15° to the left, we have the following

results: When the left edge is moved from + to =:-4.17, from = to

-:-8.5, from - to =:-1.33, from = to +:+1; when the right edge is moved

from + to =:+4.17, from = to -:+1.17, from - to =:+4.5, from = to

+:+8.67.

If the position of the eyes is 30° to the left, we find when the left

edge is moved from + to =:-2.67, from = to -:-6.67, from - to =:+0.5,

from = to +:+3.33. When the right edge is moved from + to =:+2.33, from

= to -:-0.02, from - to =:+9., from = to +:+12.33.

If we take again the general averages, we have for the eye-position of

15° to the left an equality-point of -3.25 if the left edge is moved

and judged and +4.63 if the right edge is moved and judged. That is,

if the right edge stands at 2000 mm. the left edge must be moved to

1996.75, and if the left stands at 2000, the right must be moved to

2004.63. For the eye-position of 30° to the left, the equality-point

lies at -1.49 if the left edge is moved and judged, and at +5.91 if

the right edge is the variable. The threshold lies in all three cases,

for eyes at 0°, at 15°, and at 30°, at about ±5 mm.; the position of

the eyes has thus no influence on the threshold for the perception of

distance in the direction of regard.

But the point essential for our investigation is of course not

the threshold but the equality-point. To take the extremes of the

eye-positions 0° and 30° we find the equality when the left edge is

judged, at -0.76 for 0° and -1.49 for 30°, and when the right edge is

moved, at +4.41 at 0° and +5.91 at 30°; the middle is thus +1.82 for 0°

and +2.21 for 30°, that is a difference of less than 0.4 mm.

To understand this figure we must enter into the calculation of the

angles. We have an eye-distance of 60 mm., a distance of the edges from

the cornea 2000 mm., from the nodal points 2007.4 mm., the distance of

each edge from the median line 15 mm., the distance of the two edges

from each other thus 30 mm. as long as they are in the same plane. We

have to determine the angle under which each eye sees the distance of

the two edges. A simple trigonometric calculation gives the following

figures: If both eyes are in normal position, at 0°, and both edges

are in the same plane, 2000 mm. from the corneæ, the angle for each

eye is 51' 22". If the left edge is now moved to +5, the left eye sees

the distance of the edges at an angle of 51' 25", the right eye under

51' 10", the difference is thus 15"; if the left edge is at +10 mm.,

the left eye's angle is 51' 29", the right eye's angle 50' 59", the

difference 30". If the left edge is moved to -5 mm., the left eye's

angle is 51' 18", the right eye's angle 51' 33", the difference 15";

if the left edge is moved to -10 mm., the left eye's angle is 51' 14",

the right eye's angle 51' 45", the difference 31". Now we saw that with

normal eye-position when the left edge was moved the threshold was

+5.93 and -6.97; a difference of 15" to 20" between the visual angles

of the two eyes was thus amply sufficient to give a distinct experience

of different distance. When the left eye's angle was about 15" smaller

than the angle of the right eye, the difference of the retinal images

gave a sure impression of the greater nearness of the left edge.

If we now bring the eyes into the position of 30°, the angles are of

course different when both edges are in the same plane vertical to

the direction of regard. If the two edges are in the same plane, the

left eye's angle is 50' 59" and the right eye's angle 51' 45", the

difference thus 46". If we move the left edge to +5, the left angle

becomes 51' 1", the right angle 51' 34", the difference 33". If we move

the left to +10, the left angle becomes 51' 4", the right 51' 24"; the

difference is thus still 20", and we must move the left edge to +17 mm.

to get an equal angle for the left and the right eye. If we move the

left to -5, the difference becomes of course larger, the left eye sees

under 50' 56", the right eye 51' 55", the difference 59"; and at -10,

the left eye has the angle 50' 53", the right eye 52' 6", difference 1'

13". It is hardly necessary to state here the angles for the changes of

the right edge or for an eye-position of 15°, inasmuch as the maximum

differences bring out our case most clearly. With an eye-position of

15°, the edges at the same plane give angles of 51' 10" and 51'34",

that is, a difference of 24"; if the left edge is moved to -5 mm. the

difference becomes 38"; if it is moved to -10 mm. the difference is

54"; if the left edge is moved to +5 the difference decreases to 10"

and at +10 mm. to 6".

We have thus the following fundamental result: If the eyes are in

normal primary position, a movement of the left edge to ±6 mm. is

constantly apperceived at threshold of distance and this corresponds to

retinal images whose visual angles differ by about 17". A difference

of 17" in the visual angles of the two eyes produces thus under the

conditions of this experiment for this subject a strong stereoscopic

effect when the eyes are in primary position. If the eyes are in the

position of the head 30° to the left, the left eye thus much further

from the edges than the right eye, the visual angle of the left image

thus much smaller than that of the right image, we find the same

equality-point with the same threshold. We saw that in this position

the two visual angles would be equal if the left edge were moved to

+17 mm.; instead of at +17, the equality-point--when the left edge is

judged--lies at -1.49, that is, at a point at which the visual angle

of the left eye is more than 46" smaller than the angle of the right

eye. While in normal position a difference of the two retinal images of

17" constitutes a distinct threshold value; at a lateral position of

the eyes of 30° the great difference of 46" becomes necessary to give

the impression of equal plane, while a decrease of that difference to

30" gives a distinct feeling of greater distance. Equal retinal images

produce for the lateral eyes thus the same effect which for the normal

position very different images produce; and to get for the lateral eyes

the effect which equal images produce for the normal position, the

angles of the images must differ by 46".

The results for the second subject, Mr. Flexner, are practically the

same. With the position of the eyes at 0°, when the left edge is judged

and moved, we find the following averages: from + to =: +0.03, from =

to -:-3.8, from - to =:-0.7, from = to +:+3.93; when the right edge is

moved from + to =:-0.08, from = to -:-4.29, from - to =:+1.21, from =

to +:+4.08. It is evident that the difference between right and left

which existed for Mr. Tait does not enter into Mr. Flexner's results.

The equality-point as average of 120 experiments lies for normal

eye-position practically at zero, and the threshold is ±4 mm.; his

sensibility for differences of retinal images is thus still finer than

for Mr. Tait, as we saw that the threshold of ±4 mm. means a difference

of visual angles of less than 15". If Mr. Flexner's head is turned 15°

to the left, his left eye thus considerably farther away from the edges

than the right eye, the results are these: If the left edge is moved

and judged, we find from + to =:-0.02, from = to -:-3.17, from - to

=:0, from = to +:+4.67; if the right edge is moved from + to =:-0.01,

from = to -:-2.5, from - to =:-0.8, from = to +:+3.33. Experiments

with lateral movement of 30° were not carried through, as the subject,

accustomed to eye-glasses, became less accurate in the judgments; but

the experiments with the position of 0° and of 15° are unequivocal.

They show that the equality-point and the thresholds are exactly the

same for 15´ as for 0°. For the lateral position of 15° again the

average equality-point is exactly at 0° and the threshold at less than

±4 mm. We saw that for a lateral movement of 15° the difference of

the angles at the equality-point is 24". We find thus for Mr. Flexner

that with primary eye-position a difference of angles of less than 15"

gives a distinct stereoscopic effect, while with a lateral position of

the eyes a plane effect demands a difference of 24" for the two visual

angles.

Experiments with Dr. Bell finally showed a rather strong fluctuation

of judgments and the determination of the equality-point for normal

eye-position has not only too large a middle variation to be a reliable

basis, but is influenced by a constant tendency to underestimate the

distance of the edge moved. Yet the general result is the same as with

the other two subjects, that is, the equality-point is with him, too,

practically the same for the eyes in normal and in lateral position.

The general conclusion from the results of all three subjects is thus

evidently that the traditional physiological theory is untenable, the

stereoscopic effect cannot be simply a function of the difference

of the two retinal images. The same pair of unequal retinal images

which gives a most striking stereoscopic effect for eyes in primary

position, has no stereoscopic effect for eyes in lateral position and

_vice versa_. The stereoscopic interpretation is thus the function

of both the difference of the retinal images and the position of the

eyeballs. Of course the two retinal images are in any case never

felt as two pictures if they are not different enough to produce a

double image. With the primary position of the eyes as long as the

two different retinal views are sufficiently similar to allow a

synthesis in a three-dimensional impression of our object, we perceive

every point of the object not as double image but as one point of

a given distance. The distance feeling of the normal stereoscopic

vision demands thus itself more than the reference to the different

retinal images, and the only factor which can explain the phenomena

is the response of the eye-muscles which react on the double images

by increase or decrease of convergence. The distance of a point in a

stereoscopic image is determined by the impulse necessary for that

particular act of convergence of the eyeballs by which the two retinal

images on non-cor-responding points would be changed into images on

corresponding points. The different retinal images are thus ever for

the normal eye-position merely the stimuli for the production of that

process which really determines the experience of distance, that is,

the motor impulse to a change in convergence.

If thus the stereoscopic vision under normal conditions is ultimately

dependent upon the central motor impulses, it is not surprising that

a change in the psycho-physical conditions of movement produces a

change in the resulting impulses. Such a change in the conditions is

given indeed whenever the eyes are in a lateral position. Just as

the same stimulus produces a different response when the arm or leg

is in a flexed or an extended position, so the retinal double images

stimulate different responses according to the particular position

of the eyeballs. That pair of unequal retinal images that in primary

eye-position produce in going from one end of the object to the other a

strong increase of convergence and thus a feeling of greater nearness,

may produce with the lateral eye-position no increase of convergence

and thus a feeling of equal distance or even a decrease of convergence

and thus a feeling of removal. The psycho-physical system upon which

our three-dimensional visual perception depends is then much more

complex than the usual theory teaches; it is not the retinal image of

the double eye, but this image together with the whole distribution

of contractions in the eye-muscles, which determines the stereoscopic

vision: the same retinal images may give very different plastic

perceptions for different positions of the eyeballs.

The experiments point thus to the same complex connection which

Professor Münsterberg emphasized in his studies of the "Perception of

distance."[1] I may quote the closing part of his article to bring

out the intimate connection of the two problems. He reports his

observations on the so-called verant and insists that the monocular

verant almost as little as the ordinary binocular stereoscope can give

the impression of normal distance of nature. Professor Münsterberg

writes: "Whoever is able to separate seeing in three dimensions from

seeing in natural distance cannot doubt that in both cases alike we

reach the first end, the plastic interpretation, but are just as far

removed from the other, the feeling of natural distance, as in the

ordinary vision of pictures. The new instrument is thus in no way a

real 'verant.'

"The question arises, Why is that so? If I bring my landscape picture

on a transparent glass plate into such a distance from my one eye

that every point of this transparent photograph covers for my resting

eye exactly the corresponding point of the real landscape and yet

accommodation is excluded, as, for instance, in the case of the

short-sighted eye, or in the case of the normal eye with the verant

lenses, then we have exactly the retinal images of the real view of

nature and the same repose of the lens. Why are we, nevertheless,

absolutely unable to substitute the near object for the far one? This

problem exists in spite of all the theoretical assurances that the one

ought to appear exactly like the other, and I think that it is not

impossible to furnish an answer to it.

"If I am not mistaken, there is one point of difference between seeing

the mere picture and seeing the far landscape, which has been neglected

in the usual discussions. Every one knows, of course, that we see the

picture and the landscape normally with the help of eye-movements. The

eye moves from point to point; but psychologists have neglected the

consideration that the relation between eye-movement and retinal image

must be quite a different one for the landscape and for its photograph.

Let us consider the simplest possible case, the case of the myopic eye

without any lenses whatever, and without any need of accommodation for

a picture as near to the eye as 10 cm. If I take a small landscape

picture made with a camera whose distance from lens to plate is 10

cm., I have a splendid plastic view if I see it at a distance of about

10 cm. from my eye. I have before me just such a picture in which two

mountain peaks are, in the photograph, 1 cm. distant from each other.

If I now have my little picture at the distance of 10 cm. from the

eye, these two mountain tops correspond in their distance of 1 cm.

exactly to the retinal image which the two real mountains, which are

ten miles away and one mile distant from each other, produce in my

retina. The retinal image of the two mountain peaks in the photograph

is thus for my resting eye indeed identical with that of real nature.

Does that mean that I have to make the same eye-movement to go from

the left to the right mountain in the landscape as in the picture? Of

course, that would be so, the movement would be just as identical as

the retinal images if the nodal point of the light-rays were identical

with the rotation-point of the eyeball. But everybody knows that this

is not at all the case. The light-rays cross in the lens. The angle

of vision, and thus the size of the retinal image, are thus dependent

upon the distance of the lens from the retina. But the movement of the

eye is related to a rotation-point which lies about 13 mm. behind the

cornea, roughly speaking 1 cm. behind the nodal point of the rays. This

additional centimetre plays, of course, no rôle whatever, if I look at

my mountains in the real landscape; following with my eyeball from the

fixation-point of the left mountain to the fixation-point of the right

mountain, I make a movement whose angle can be declared identical with

the angle under which I saw the two mountains with the resting eye in

the first position. This angle of vision was determined by the distance

of the nodal point, which was in our case ten miles, while the angle

of eye-movement was determined by the distance of the rotation-point,

which would be ten miles plus one centimetre, and there is of course

no possible difference for practical discrimination between these two

distances.

"But the situation is completely changed if I turn to my little

picture 10 cm. distant from my eye. The angle under which I see my

two peaks is, of course, again the same under which I saw them in the

real landscape. It is determined by the distance of the picture from

the nodal point, which is in this case 10 cm. But the angle of the

eye-movement necessary to fixate first the left and then the right

peak is now a much smaller one because it is again determined by the

distance from the rotation-point, and that is in this case 10 cm.

plus 1 cm. With this short distance of the picture from the eye this

one additional centimetre is not at all the negligible quantity which

it was in addition to ten miles in the landscape. For the two real

mountains the angle of the eye-movement had a tangent of one tenth;

for the photograph mountains, in spite of their equal size of retinal

image, the angle of necessary movement would of course have a tangent

of one eleventh. Roughly speaking, we could say that the photograph,

in order to produce the same eye-movement which the mountains in the

landscape excited, would need a pictorial distance between the two

photograph mountains of 11 mm. instead of 10 mm. Of course if the

distance in the picture were made 11 mm. instead of 10, it would not

cover any more the mountains of the landscape. The retinal image would

thus be relatively too large and would not give us any longer the true

landscape. On the other hand, if we tried to correct it by bringing the

picture one centimetre nearer to the eye, then of course every retinal

image would be enlarged by that necessary tenth, and yet there would be

no help for the situation, as now again the eye-movement demanded by

the retinal image would be relatively increased too.

"We can put it in this way: _my real landscape demands a relation

between retinal image and movement which my picture cannot produce

under any circumstances whatever_. That which would be needed to

imitate the relations would be realized only if I had my retinal

images from the picture at a distance of 10 cm., and at the same time

the movements belonging to the same picture seen at a distance of 9

cm. That is of course unrealizable. We cannot see a picture without

having our movements constantly controlled by the size of the real

retinal images, as it is necessary that the distance seen in indirect

vision is the distance covered by the fixation-point during the

eye-movement. That demands, as we have seen, a different relation

between retinal image and eye-movement for near and far, and no verant

and no stereoscope can eliminate this factor. If a 10-mm. object in the

photograph demands an 11-mm. movement to give the impression of real

natural distance, then we have a condition which cannot be fulfilled.

"If we remember how extremely delicate is our normal sensitiveness for

retinal distances and how the newer studies in stereoscopic vision have

demonstrated an unsuspected delicacy of adjustment between retinal

images and motor responses, it is evident that this so far always

neglected relation must be an extremely important one. If we have

one adjustment of central reaction in which a certain eye-movement

corresponds to retinal images of one size, and another adjustment in

which the same movements correspond to retinal images which are ten

per cent larger, we can really not expect our judgment of distance

to neglect the difference between these two systems of relations. Of

course they represent two extreme cases. Every distance beyond 10 cm.

demands its special adjustment up to the point where the distance

becomes too large to be influenced by the distance from the nodal point

to the rotation-point. We must thus presuppose a sliding scale of ever

new adjustments for the different distances at which we see any object,

and we have, in this relation, probably not the least important factor

in the judgment of the third dimension for relatively near objects, and

probably even more important than the irradiation circles which control

the accommodation, as these circles must be the same for objects which

lie before and behind the fixation-point. Of course the whole system

of our localizing reactions becomes through these considerations more

complex by far than the schematizations of the text-books propose. But

physiological optics has shown at every point in its development that

mere simplification has not always meant a deeper insight into the real

relations."

It is evident that our studies in stereoscopic vision with lateral

eye-position involve exactly the same principle and reaffirm completely

Professor Münsterberg's theoretical views. In both cases, in the

monocular of the verant as in the binocular of our experiments, the

same retinal image has different psycho-physiological space-value on

account of the different motor situation.

FOOTNOTE:

[Footnote 1: Münsterberg: Perception of Distance, The Journal of

Philosophy, Psychology and Scientific Methods, vol. 1, p. 617, 1904.]

EYE-MOVEMENTS DURING DIZZINESS

BY E. B. HOLT

It is a familiar fact that when the head is passively turned about

its vertical axis, the eyes do not move with the head but lag behind,

keeping their fixation on that object toward which they were directed

before the head moved. The eyes move in their sockets in a direction

opposite to that in which the head has moved. Now it has been proved

beyond a doubt by the experiments of Mach,[2] Crum Brown,[3] and

Breuer,[4] that these lagging movements of the eyes are reflex and are

governed by the semi-circular canals, which are stimulated directly by

the motion of the head. Similar reflex eye-movements are found when the

head is turned about some other than its vertical axis, the direction

of such movements being always in confirmation of the theory. All

these movements, together with the theory, are well described in the

summaries of Peters[5] and Nagel.[6] The present paper deals solely

with the eye-movements that occur after rotation of the head about its

vertical axis.

The mechanism of these lagging, reflex movements is not, then,

identical with that which enables us, when the head is at rest, to

fix on and follow a luminous moving object,--the "pursuit movements"

of Dodge.[7] It is, however, identical with that of Dodge's "fourth

type"[8] and that of the compensatory eye-movements described

by Brown,[9] Nagel,[10] and Delage,[11] and recently studied by

Angier.[12] This function of the semi-circular canals was first

suggested by Goltz in 1870. Now if the rotary movement of the head is

prolonged, the eyes lag for a while on their first fixation-point, and

then dart suddenly forward to a new fixation-point on which they rest

for a while as before, until they dart forward again. Therefore if the

head continues to rotate, the eyes fall into a regular and well-marked

nystagmus. In this the lagging movements, or those opposite to the

direction of the head, are called "compensatory," and are relatively

slow and long. Their rate coincides closely if not exactly with that

of the head-movement. But the movements forward, in the direction of

the head-movement, are short and swift. Such are the facts during the

rotation of the head.

But if this rotation has been somewhat prolonged, the ocular nystagmus

continues after the head and body are brought to rest. But now its

phases are reversed, and the slower eye-movements are in that direction

in which the head has moved; while the swifter are in what before

was the lagging direction. These observations are in accord with

the semicircular canal theory, and are well established by various

investigators.[13]

This paper presents the results of a photographic study of the reflex

eye-movements following after rotation of the head (and body) about the

vertical axis.

The subject whose eyes were to be photographed sat in a chair placed

on a rotating platform, in such a position that the vertical axis of

rotation passed through, or just posterior to the nose. Rays from an

arc-lamp of 6 amperes, placed about 60 cm. from the subject's face,

were so converged by a lens that when the subject came to rest, after

the rotation, his two eyes were brightly illuminated. An adiathermal

screen consisting of a dilute solution of copper ammonium sulphate

kept the heat from being painfully intense on the eyes. The light fell

slightly from one side on the subject's face, when he was brought to

rest; and directly in front of him, at a distance of about 40 cm., was

a camera of which the lens was on a level with his eyes. The ordinary

ground-glass screen at the back of this camera was replaced by a

light-proof box, in the front of which, and in the plane which should

have been that of the ground glass, was a slit 55 mm. broad and 5 mm.

high. Inside the box was a Ludwig kymograph of which the drum rotated

on a horizontal axis: the circumference of the drum lay tangentially

to the front of the box, and the line of tangency passed horizontally

through the long axis of the slit. For each photograph a photographic

film of sensitometer 40 was fixed to the drum, as paper is ordinarily

fastened, and in moving, the drum carried this film upwards past the

slit. It follows from this arrangement that 5 mm. along the length of

this film were always exposed at once. The camera was so focused that

the images of both eyes were sent through the slit, and fell on the

film.

[Illustration: Figs. 1 and 2]

The subject's head was rigidly held by a rest: this rest was adjusted,

and the camera focused, before the rotation. The adjustment of the

head was greatly facilitated by fastening a fine black thread to pegs

that projected forward from the head-rest, on either side; the thread

was stretched horizontally, and at such a height that its image in the

camera coincided with the middle of the long (horizontal) axis of the

open slit. If then the subject, on seating himself in the chair, had

his head so adjusted that each eye was directly behind the thread,

each eye would certainly be imaged on the sensitive film. Neither the

shadow of this thread on the subject's face, nor its image on the film,

interfered in the least with the exposure that was made after rotation.

This thread was further found very useful by the subject himself,

who, after the rotation and just before the exposure was made, could

make sure by sighting on the thread that his eyes had not slightly

changed position during the rather protracted rotation. The subject was

ordinarily turned twenty-five times at about the rate of one turn in

two seconds. The kymograph was set in motion and the exposure commenced

as soon as the whirling chair was brought to a dead stop. This stopping

always took two or three seconds, at the very time when the nystagmus

was most pronounced, so that the photographs do not show the maximum

eye-movements. The exposure lasted through one rotation of the drum,

nine seconds.

In the strongest negatives the movements of the eyes can be fairly

well made out from the undulatory curve generated on the film by the

dark image of the iris as it oscillated from side to side. But this is

true only of the best negatives, and almost never of these if the eyes

photographed had the iris blue. In order to obtain better definition

in the photographs of the eye-movements, small flecks of Chinese white

were tried, as invented and described by Judd.[14] A small square of

white was laid with a brush on each cornea, on the side toward the

lamp, so that its image on the film should be as bright as possible.

The flecks were found to adhere to the eyeball even more perfectly than

Judd himself has claimed; and they produced so little discomfort that

the subject ordinarily forgot their presence on the eyes. Nevertheless

their image as produced on the negatives, although much better than

that of the iris, was generally not clearly readable, owing to the

brief exposure and the illumination by electric light. This light seems

not to be well reflected by the Chinese white: but in all cases where

daylight can be employed the use of these flecks must be eminently

satisfactory.

Thus it was found necessary to fall back on the image of the arc as

reflected from the cornea. This corneal image invariably traced a

clear, strong curve on the negative, and would have been appropriated

at the outset, were it not that its movements are not, as is well

known, a true register of the _amplitude_ of the corresponding

eye-movements; a fact that was shown clearly from a comparison in

these negatives of the curves produced respectively by the flecks

of Chinese white and by the corneal image. The former showed a much

greater amplitude of movement. But the corneal reflection is a perfect

register of the _time_ and _direction_ of the eye-movements; and in

the following tables these features alone are studied. This reflection

traced on the film a perfectly readable curve, although in some of the

films, owing to a shifting of the carbons in the lamp taking place

during the rotation, one of the eyes would be badly illuminated and a

good record would be obtained from the other eye alone.

The arc ran on an alternating circuit of 60 phases per second, and

owing to these interruptions of the illumination the curve of the

corneal image showed on the negative as a dotted line in which the

distance between any two dots represented one sixtieth of a second.

Since the constancy of this alternation in the current has been

measured in the Jefferson Physical Laboratory (of Harvard), and found

to vary within a few tenths of one per cent only, the spacing of the

dots on the negatives formed the most convenient possible means for

determining the durations of the nystagmiform movements. These dots are

shown in Figs. 3, 4, and 5 (Plates I and II).

[Illustration: PLATE I.

Fig. 3

(By an error Fig. 4 is shown reversed; the lettering is correct.)

Fig. 4]

Fig. 3 shows a portion of one of the films. The two curves are to be

read from below upwards; but at the bottom is a photograph of the slit

(showing a part of the subject's face) taken when the drum had made

a little over one revolution and had come back to rest. Hence below

the image of the slit, the curve of corneal reflection is doubled.

"Right" and "Left" refer to the subject's right and left sides, so

that the reader looks into the subject's face from in front. In the

picture of the slit, the place on the cornea of the corneal reflection

is shown; and also a minor reflection, which as may be seen traced no

curve, from some other source of light. The fine line that crosses

the slit horizontally is the image of the thread, above mentioned,

which was used in adjusting the head. The time-dots are seen to be

perfectly distinct, so that they could be accurately read with the

help of a jeweller's eyeglass. Fig. 4 shows another part of the same

negative, a portion subsequent to the single eye-curves of Fig. 3,

that is, a continuation vertically upwards of Fig. 3. The rotation

had been from the subject's left to his right, a direction that will

be termed "clockwise" throughout this paper, and it can be seen that

the quick eye-movements are toward the subject's _left_, while the

slow are towards his right: had the photograph been taken _during_ the

rotation, the directions of the quick and slow movements would have

been reversed. Two points may be observed in this figure which the

tables will also bring out,--that the two eyes move together, and that

as the nystagmus subsides the quick eye-movements become less frequent

but endure no longer, or in other words, the slow movements alone

increase in duration. The corneal reflection does not accurately show

the amplitude of the movements; but direct inspection of a subject's

eyes, as the nystagmus dies away, shows that generally (but perhaps

not always) the amplitudes of both quick and slow movements decrease

together. When this is the case, it follows that at the end of the

nystagmus the _rate_ of the slow movements decreases very much faster

than that of the rapid movements.

Readable negatives were obtained from four, out of six subjects. Of

such negatives there are fourteen, ten of which are of eye-movements

after rotation clockwise, and four after rotation anti-clockwise.

This distribution is accidental, for the rotations in each direction

were about equal in number. With the exceptions to be noted later all

the negatives exhibit the same features, so that of the fourteen only

four examples are given in full in the tables; while for the others

merely the averages of the duration of quick and slow eye-movements

respectively are given.

TABLE I

KEY:

1: Subject

2: Film

3: Eye

4: Direction of the rotation.

5: Slow movements toward Subject's

6: Rapid movements toward Subject's

7: Average duration in seconds of slow movements

8: Average duration in seconds of rapid movements

1 2 3 4 5 6 7 8

C 1 left clockwise right left .32 .05

" 2 " " " " .36 .06

" 3 right anti-clock left right .26 .08

H 1 " clockwise right left .54 .07

" 2 " " " " .45 .07 }

" " left " " " .45 .07 }

" 3 " " " " .50 .08}

" " right " " " .49 .08}

" 4 " anti-clock left right .49 .07

" 5 left clockwise right left .53 .06

Ta 1 right " " " .73 .07

" 2 " anti-clock left right .48 .10

Tu 1 " clockwise right left .50 .06 }

" " left " " " .49 .07 }

" 2 " " " " .49 .12}

" " right " " " .49 .12}

" 3 left " " " .40 .07

" 4 right anti-clock left right .58 .08

Av. .48 .08

Table I gives these averages for all the fourteen negatives. In four

of these (H 2, H 3, Tu 1, Tu 2) simultaneous curves for both eyes

were obtained. In every curve the slow eye-movements were in the

same direction as the previous rotation; the rapid in the opposite

direction. The very few single movements that are exceptions to this

are noted under Table II. Had the photographs been taken during

(instead of after) the rotation, the directions of rapid and slow

movements would undoubtedly have been reversed. It is to be noted

that when both eyes were recorded, their movements were generally

identical, within the accuracy of measurement (one sixtieth of a

second). There are a few exceptions to this. The averages of all slow

and all rapid movements merely show that in general, and for that part

of the nystagmus that was photographed, the slow eye-movements lasted

six times as long as the rapid ones. This ratio varies considerably

from one case to another, and at best throws little light on the whole

nystagmiform series, since during the very first instants after the

rotation the ratio of quick to slow movements would be less than one

sixth, and at the very end of the series would be considerably more;

this because toward the end the slow movements become much slower,

while the rapid seem to change very little. The variations from case

to case arise, at least partly, because in some cases the picture was

taken more promptly, after the rotation stopped, than in others.

TABLE II

All records in seconds.

Subject C. Subject H. Subject H. Subject Tu.

Film 3. Film 2. Film 3. Film 4.

anti-clockwise. clockwise. clockwise. anti-clockwise.

right eye. left eye. right eye. left eye. right eye. right eye.

slow fast slow fast slow fast slow fast slow fast slow fast

m. m. m. m. m. m. m. m. m. m. m. m.

to to to to to to to to to to to to

lft. rt. lft. rt. lft. rt. lft. rt. lft. rt. lft. rt.

.26

.08 .03 .05 .06 .08 .06

.2 .51 .58 .1 .1 .45

.06 .06 .06 .06 .05 .08

.05 .16 .16 .13 .13 .75

.08 .05 .06 .1 .13 .06

.19 1.01 1.05 .36 .33 .36

.05 .06 .06 .1 .06 .13

.02 .26 .26 .28 .3 .48

.05 .05 .06 .13 .13 .05

.21 .26 .26 .28 .23 .61

(.19) .06 .06 .11 .13 .1

.16 .55 .6 .35 .35 .41

.05 .1 .1 .08 .1 .05

.03 .25 .25 .33 .3 .65

.05 .06 .05 .06 .11 .06

.18 .33 .33 .25 .2 .51

.06 .1 .1 .1 .1 .05

.03 1.65 1.65 .83 .83 .66

.05 .06 .06 .1 .13 .16

.29 .26 .26 .63 .61 .66

.11 .06 .08 .06 .06 .08

TABLE II, _continued_.

All records in seconds.

Subject C. Subject H. Subject H. Subject Tu.

Film 3. Film 2. Film 3. Film 4.

anti-clockwise. clockwise. clockwise. anti-clockwise.

right eye. left eye. right eye. left eye. right eye. right eye.

slow fast fast slow fast slow fast slow fast slow slow fast

m. to m. to m. to m. to m. to m. to m. to m. to m. to m. to m. to m. to

lft. rt. lft. rt. lft. rt. lft. rt. lft. rt. lft. rt.

.29 .78 .76 .45 .43 .68

.03 .06 .06 .05 .1 .15

.04 .16 .2 .45 .43 .23

.05 .1 .1 .06 .1 .11

.25 .38 .33 .4 .38 .36

.15 .08 .11 .08 .06 .08

.3 .58 .56 .58 .56 .35

.05 .06 .06 .06 .06 .06

.33 .78 .78 .58 .56 .38

.05 .08 .1 .08 .08 .05

.28 .71 .71 .35 .35 1.78

.11 .08 .06 .05 .06 .06

.41 .46 .45 .51 .5

.06 .05 .06 .06 .05

.43 .56 .58 .6 .61

.11 .06 .06 .08 .1

.35 .33 .31 .73 .68

.05 .1 .1 .06 .06

.23 .86 .86

.15 .08 .08

.38 .21 .21

.1 .06 .05

.43 .8 .81

.11 .08 .08

.38 1.53 1.58

.03 .06 .05

.53

.2

.23

(.18)

.36

.03

.23

.06

.45

.11

.25

Averages

.26 .08 .07 .45 .07 .45 .08 .50 .08 .49 .58 .08

Parentheses indicate time during which the eye did not move at all.

[Illustration: PLATE II.

Fig. 5]

Table II gives in detail the data yielded by four of the most

instructive films. C 3 is the longest record that was obtained; Tu 4

is among the shortest, though it is not the very shortest. H 2 and

H 3 show how nearly alike are the simultaneous movements of the two

eyes: .07 sec. is the greatest difference recorded on any film between

simultaneous movements. All four records show how much less the

duration of the slow movements is at the beginning of the record than

at the end, and how little the fast movements vary in this respect.

H 2 is given because it is not typical; and about one half of the film

itself is reproduced in Fig. 5 (Plate II). It will be seen that at four

points there intervened between slow movements (toward the right) a

rapid one that was also toward the right. This is the only record in

which such a thing happened: and its explanation is problematical. With

the subjects C and H, and only very rarely with these, a rapid movement

sometimes took the place of a slow one, that is, occurred in the same

direction as the slow movements (_e. g._, Table II, C 3). And a trifle

more often, yet very seldom, a rapid movement was relatively slow (_e.

g._, _ibid._). With every subject there are a few cases in which the

eyes stood still for a small part of a second (_e. g._, _ibid._), and

these moments of rest seem to come after a rapid or a slow movement

indifferently.

McAllister[15] and others have shown that the eyes are seldom at rest

even when voluntary fixation is attempted, and these anomalies in the

nystagmiform series may well be the result of such random factors,

which instead of being always inhibited by the afferent impulses from

the semicircular canals, which govern the nystagmus, operate along with

these latter, and sometimes even inhibit them. With the exception of

these anomalies, the movements recorded in the photographs confirm the

observations of Purkinje, Mach, Breuer, Delage, and other investigators.

In conclusion, the sensations of vertigo and of nausea seem not to be

essentially connected with the nystagmus. Several subjects were so

disagreeably affected by a preliminary rotation that it seemed best not

to continue the experiment with them. With those, however, whose eyes

were photographed, while they experienced a mild degree of vertigo and

nausea during and after the first few rotations, these sensations soon

wore off with further practice, while so far as could be observed their

eye-movements were as ample and rapid as at first. The introspection

of these subjects was that after the rotation the body seemed at rest

and the stomach quite settled, while the visual field alone whirled

rapidly in the direction opposite to that of the previous rotation.

FOOTNOTES:

[Footnote 2: E. Mach: Sitzungsb. d. k. Akad. d. Wissensch., Wien, 1874.]

[Footnote 3: A. Crum Brown: Proceedings of the Royal Soc., Edinburgh,

1874.]

[Footnote 4: J. Breuer: Med. Jahrb., Wien, 1874-75.]

[Footnote 5: W. Peters: Arch. f. d. ges. Psych., vol. 5, p. 42, 1905.]

[Footnote 6: W. Nagel: Handbuch d. Physiol. des Menschen, vol. 3, p.

762, 1905.]

[Footnote 7: R. Dodge: Amer. Jour. of Physiol., vol. 8, p. 317, 1903.]

[Footnote 8: _Ibid._ p. 327.]

[Footnote 9: A. Crum Brown: Proceedings of the Royal Soc., Edinburgh,

1895.]

[Footnote 10: W. Nagel: Zeitsch. f. Psych. u. Physiol., vol. 12, p.

331, 1896.]

[Footnote 11: Yves Delage: Arch. de Zoöl. expér. et générale, vol. 1,

1903.]

[Footnote 12: R. P. Angier: Zeitsch. f. Psych. u. Physiol., vol. 37, p.

235, 1905.]

[Footnote 13: See the summaries of Nagel and Peters, above referred to.]

[Footnote 14: C. H. Judd: Yale Psych. Studies, Psych. Rev., Mon.

Supplements, vol. 7, no. 1, p. 7, 1905.]

[Footnote 15: C. N. McAllister: Yale Psych. Studies, Psych. Rev. Mon.

Supplements, vol. 7, no. 1, p. 17, 1905.]

VISION DURING DIZZINESS

BY E. B. HOLT

During and after a prolonged rotation of the head, the visual field

seems to spin around before one's eyes,--a phenomenon that is

ordinarily called the "dizziness of Purkinje." Delage describes it as

follows:[16] "In the experiment of Purkinje, while we are rotating in

a positive sense, space seems possessed of a motion in the opposite

direction.... This phenomenon is explained _by the direction of the

nystagmus_."

"In the nystagmus," he continues, "the eyeballs execute two

well-differentiated motions: one, a compensatory, _relatively_ slow

motion, during which images pass across the retina so as to give the

appearance of a movement of space in the opposite direction; two, a

swift motion opposite to the slow one, and so rapid that the images

passing across the retina leave no sensation of their movement."

Now, in a previous paper[17] I have shown that there is a central

anæsthesia, or central inhibition of visual sensations, during about

the latter two thirds of the time occupied by every voluntary eye-jump;

and in view of this I was led to enquire whether in fact, as Delage so

confidently asserts, it is the _speed_ of these more rapid movements,

or some other factor, that causes them to leave no visual sensations.

There can be no doubt that they do leave none, since, aside from the

statement of Delage, in dizziness the visual field whirls always in

only one direction; whereas it should otherwise appear to swing now

to one side, now to the other, as the eyes move back and forth across

the objects. I have found but one other mention of this point in the

literature. In his Analyse,[18] Mach says, parenthetically, "(the

jerky eye-movement leaves no optical impression)"; but he does not

suggest that this is because of its greater speed.

In order to test this point, a 2 c. p. incandescent lamp was so

arranged that it could be moved vertically in front of, and about four

metres distant from, a rotating chair. Since after a rotation the eyes

are oscillating from side to side, if the lamp is moved up and down an

obliquely inclined after-image streak must be generated on the retina;

and clearly there are four possible positions in which this may lie, as

shown in Fig. 1.

The results were absolutely uniform (the author alone as subject);

the after-image streak always lay on that side of the moving light

_toward_ which the _slow_ eye-movements were directed, that is, the

lamp appeared to drift obliquely up or down and in a lateral direction

_opposite_ to that of the slow eye-movements. Apart from its vertical

displacement, then, the lamp behaved like the less intensely illumined

parts of the visual field, seeming to be totally invisible during the

swifter eye-movements. Now since the experiment was done in a partially

darkened room and the eyes were partly adapted to darkness, the lamp

should have been intense enough adequately to stimulate the retina

even during the more rapid movements, and might be expected to leave

an after-image streak on that side toward which these rapid movements

were directed, and differing only from the streaks seen during the slow

eye-movements in being inclined at a less angle from the horizontal.

Yet no such streaks were visible.

These observations were made at about the same number of seconds after

the rotation stopped, as the photographs were taken that are recorded

in the preceding paper of this volume. The rapid movements were

therefore about one sixth as long in duration as the slower ones. Since

the respective amplitudes of rapid and slow must average very nearly

the same, the rapid movements must have been about six times as swift

as the slow movements. It needs therefore to be shown beyond a doubt

that the 2 c. p. lamp _was_ bright enough, in view of the briefness of

stimulation of any one retinal element during the rapid eye-movement,

to be above the threshold of perception. For this reason the experiment

was not continued with other subjects.

The certainly adequate degree of illumination was realized during the

photography of the eyes described in the preceding paper. Here during

the post-rotary dizziness an arc lamp (of 6 amp.) was in front of

the face and but a little to one side of the primary line of regard;

it was 60 cm. distant from the eyes and on a level with them; a lens

condensed the rays on the two eyes, and the light was diminished

only just enough as not to be painful, by a dilute screen of copper

ammonium sulphate about 3 cm. thick. Of course such an illumination

must adequately stimulate each retinal element even during the most

rapid eye-movements. Nevertheless with the four subjects that were

photographed the arc lamp, like the rest of the visual field, seemed

always to swim in one direction, and that opposite to the slower

eye-movements. In one case where the eyes were photographed without the

adiathermal screen, and the light was rather painfully intense, the

lamp was still seen to drift in one and the same direction. There was

never any trace of its moving to and fro, as there should have been had

it been visible during both phases of the nystagmiform movements.

[Illustration: Fig. 1]

This absence of visual sensation during the more rapid eye-movements

might conceivably depend on either peripheral or central inhibitory

factors. But the anatomy and physiology of the eye offer no point of

support for the supposition that during such movements the irritability

of the rods and cones is momentarily reduced, or that the retinal

layers posterior to the rods and cones suffer an interruption of

function during a movement of the eyeball in its socket. Indeed, during

some such movements, the "pursuit" movements (Dodge's second type),

vision is unimpaired.[19] In view of these facts, and of the many known

cases of the mutual inhibition of sensations where undoubtedly the

process is a central one, it is by far most probable that this visual

inhibition is also a central process; as was certainly the visual

inhibition during voluntary eye-jumps, previously reported by me.[20]

The conclusion above reported that the visual inhibition during the

more rapid phase of the nystagmus in no wise depends on an inadequate

stimulation of the retina, due to the greater speed of the rapid

movements, and that the inhibitory process is purely central, is

further supported by the following phenomenon. If before the rotation

has commenced, the eyes are so strongly stimulated that a lasting

after-image is obtained, this after-image will, during the rotation,

always be seen to swim in the direction opposite to the rotation, that

is, _with_ the _slow_ eye-movements; but when the rate of rotation

begins to decrease, and as Mach, Breuer, and Delage have shown, the

slow eye-movements reverse their direction, the after-image also

reverses its direction, and now swims in the direction of rotation,

that is, _still with_ the _slow_ eye-movements. If the after-image

persists long enough, it may still be observed, after the rotation

has ceased, swimming in the same direction as the surviving slow

eye-movements. If, for instance, the slow movements are from left to

right, the after-image (best seen with the eyes closed) swims from the

left to the right hand side of the field and disappears, reappears at

the left and swims again toward the right, and continues to do this

until the nystagmus entirely ceases.

This experiment was repeated several times, with four subjects, and

with both clockwise and anti-clockwise rotations, and the results were

uniformly as described above. In order to see whether this motion of

the after-image really depended on the slower nystagmiform movements,

the following variation was tried. It will be recalled that if the

head is rotated not about a vertical (longitudinal) axis, but about a

transverse axis, as, say, one passing through the ears, a nystagmus

is produced in which during the rotation the slower eye-movements are

opposite to the direction of rotation, while when the rotation is

checked or stopped, the nystagmus, as before, reverses. The same is

true if the rotation is about a sagittal axis. These conditions were

approximately realized by having the subject sit as before on the

rotary chair, but during the rotation hold his head horizontally to

the right or left, forward or back. With any of these positions of the

head, however, the rotation produced, on all of the subjects tried,

extreme dizziness and a feeling of nausea that lasted in some cases

for several hours. This fact made it impossible to ask for a set of

the four possible positions of the head from any of the subjects. The

following are the records that were obtained:

Subject Fl. Head horizontally to left; rot. anti-clockwise.

During rot.; after-im. moved clockwise, _i. e._, from

subject's brow to chin.

Eye-mov. not observable during rot.

After rot.; after-im. moved anti-clockwise, chin to brow.

Slow eye-mov. anti-clockwise, chin to brow.

Vis. field clockwise, brow to chin.

Subject H. Head horizontally to right; rot. anti-clockwise.

During rot.; after-im. clockwise, chin to brow.

Eye-mov. not observable.

After rot.; after-im. anti-clockwise, brow to chin.

Slow eye-mov. anti-clockwise, brow to chin.

Vis. field clockwise, chin to brow.

Subject H. Same repeated, with same results.

Subject H. Same as case of Fl., with identical results.

Subject K. Head horizontally to left; rot. anti-clockwise.

During rot.; after-im. not observed.

After rot.; after-im. anti-clockwise, chin to brow.

Slow eye-mov. anti-clockwise, chin to brow.

Vis. field not observed.

So far as these records go, they entirely confirm the results of other

investigators as to the direction and the reversal of the nystagmus. In

each of the cases the after-image moved with the slow eye-movements,

reversing its direction with these slow movements, while the visual

field whenever it was observed (the eyes were kept closed during the

rotation) moved in the opposite direction to that of the after-image

and the slow eye-movement. It is well known that after-images move

_with_ every involuntary eye-movement, and although they disappear

during voluntary eye-jumps,[21] they reappear at the end of the jump in

a position that is related to the new fixation-point exactly as the old

position was to the former fixation-point. These after-images, then,

are seen during the slow eye-movements whose direction they follow;

but are not seen during the quick movements, when they must naturally

move in the direction of these quick movements. And aside from this it

is possible to observe introspectively that the after-image disappears

at that side of the visual field toward which the slow eye-movements

tend, and is for a moment invisible before it reappears on the other

side of the field. As was shown above, the visual field always moves

opposite to the direction of the slow eye-movements, as must of course

be the case if there is no inhibition of vision during these movements.

The simultaneous appearance of the after-image moving with, and the

rest of the visual field moving contrary to, the direction of the slow

eye-movements, with a uniform absence of the converse phenomena, seems

to prove that vision is unimpaired during these slow movements, while

it is completely inhibited during the rapid phases of the nystagmus.

Purkinje himself[22] called the slower phases "involuntary and

unconscious," meaning by "unconscious" not that the visual field was

not seen (for it just then is seen), but that the movement of the

eyeball during the slow phases was not felt. I have observed, with

the confirmation of several subjects, that _this_ movement can also

not voluntarily be inhibited; whereas the swift movement is so far

voluntary that it can be inhibited at pleasure. It is possible, that

is, to fix the eyes on that side of the field toward which the slow

movements are directed, but not on any point at the other side of the

field. The slow movements, then, during which vision is possible, are

purely reflex. These slow movements, purely reflex and yielding clear

vision, with the rapid movements, partly under voluntary control and

attended by an inhibition of vision, present a parallelism, that may

be not without significance, to the "pursuit" eye-movements (Dodge's

"second type"), that are likewise relatively slow, are reflex, and

yield remarkably clear vision, and the ordinary voluntary eye-jumps

(Dodge's "first type"), that are relatively rapid, and are, like the

rapid nystagmiform movements, attended by a central inhibition of

vision.

FOOTNOTES:

[Footnote 16: Yves Delage: Physiol. Studien über d. Orientirung

(Aubert's transl.), p. 100, Tübingen, 1888.]

[Footnote 17: E. B. Holt: Harvard Psych. Studies, Psych. Rev. Mon.

Supplements, vol. 4, p. 1, 1903.]

[Footnote 18: E. Mach: Analyse der Empfindungen, 2d ed., p. 98, Jena,

1900.]

[Footnote 19: R. Dodge: Amer. Jour. of Physiology, vol. 8, p. 317,

1903.]

[Footnote 20: E. B. Holt: Harvard Psych. Studies, Psych. Rev. Mon.

Supplements, vol. 4, p. 42, 1903.]

[Footnote 21: S. Exner: Zeitschrift für Psych. u. Physiol., vol. 1, p.

46, 1890; E. Fick and A. Gürber: Berichte d. ophth. Gesellschaft in

Heidelberg, 1889; E. B. Holt: _op. cit._ p. 4.]

[Footnote 22: Purkinje, 1825; reprinted in Aubert's Physiol. Stud. über

d. Orientirung, p. 117, Tübingen, 1888.]

VISUAL IRRADIATION

BY FOSTER PARTRIDGE BOSWELL

There are various kinds of visual irradiation, of which perhaps the

best-known variety is that which appears as the enlargement of a

brightly illuminated surface at the expense of a contiguous one of less

intensity. This has been until recently the only form recognized, and

until very lately the greater part of the literature has dealt with it

alone.

The whole subject was carefully investigated by Plateau in 1831,

and retinal irradiation extricated from phenomena which very often

accompany it. He showed that the extent of irradiation varies with

the intensity of the stimulating light and the time during which it

is allowed to act. He was also the first to call attention to the

phenomenon of so-called negative irradiation.

Somewhat later Volkman again called attention to negative irradiation,

while Aubert, in opposing the explanation advanced by Volkman, first

showed the relations existing between irradiation and contrast.

Dove was the first to investigate the influence of irradiation on

stereoscopic pictures, thus calling attention to the question of

binocular irradiation. Experiments in this direction, however, have

in general given negative results in so far as any enlargement of the

binocular portion is concerned.

Helmholtz examined the manner in which the stimulation at the

border-line between a light and dark field changes in intensity,

and drew a curve showing these modifications of intensity due to

irradiation. Hering showed that the form of the Helmholtz intensity

curve would be modified by the presence of other phenomena not strictly

those of irradiation.

De Roux demonstrated the difference in the extent of a real induction

on the foveal and the extra-foveal parts of the retina.

Charpentier has attempted to carry forward the general explanation

by saying that this spreading of neural excitation, the existence of

which he proves to be beyond question, takes the form of an undulatory

excitation in the free nerve-endings of the retina. Bidwell has

investigated more thoroughly in some respects than Charpentier the

phenomena of the after-images of moving sources of light, which have

bearing upon irradiation. The same is true with regard to McDougall,

von Kries, Hess, and others. Burch has instituted investigations

along these lines, especially concerning the inhibition of stimuli

on contiguous portions of the retina. Hess has worked carefully

upon the different phases of the stimulation derived from a moving

source of light, the differences in functioning of the foveal and

extra-foveal parts of the retina, the respective functions of the

rods and cones, and in connection with this, made investigations in

the visual perception of color-blind subjects. All these observations

have important bearing on irradiation, contrast, and theories of

color-vision.

In connection with some work which was being done upon the after-images

of moving sources of light in the Harvard laboratory in the early

winter of 1903, some phenomena were observed which I believe are due to

one form or other of visual irradiation. They can be seen in various

ways, perhaps most advantageously by observing with fixed eyes the

passage of a luminous image over the retina. What one sees as such a

figure moves by is a travelling band of light, its forefront somewhat

like that of the stimulating source, the rest composed of a long

train of after-images which differ very decidedly from one another

in intensity and color. The advantage of this well-known method of

observation lies in the fact that it enables one to translate the

temporal relations between the different phases of the stimulation

into spatial relations between the different portions of the moving

band of light. For since the figure moves across in a plane before the

observer, that which appears in his consciousness first in time will

likewise appear as foremost on the plane in space. Thus by observing

the train of images one practically sees the different phases of

the stimulation spread out in order before one. The new phenomena

we observed, however, have to do with but a single phase of the

stimulation, the extreme front of the stimulating image.

The intensity of light used varied considerably with the differently

colored images, and was regulated so as to give as well as possible

the phenomena we wished to study. With white light the intensity was

less than that of an eight-candle-power electric lamp placed about ten

feet distant from the observer. When colored light was employed it was

necessary to use a very much stronger source of illumination, since

the colored glass which was used absorbed a great deal of light and

in case of colors lying toward the violet end of the spectrum greater

luminosity seemed demanded.

The apparatus used consisted of a three-foot pendulum with a screen

attached. This screen swung with the pendulum. In the screen was an

opening about four inches wide and three inches high, into which

strips of cardboard or tin backed by a piece of ground glass could be

slipped. In these strips differently shaped holes were made through

which the light passed. In this manner an image of any desired form

might be used. Behind the screen, between it and the lamp, was a frame

in which other pieces of ground or colored glass were placed. These

pieces of ground glass would reduce the intensity of the light and

diffuse it evenly over the image. The observer sat ten feet away. When

the pendulum was set in motion, the image would appear moving back and

forth in an arc. In order to shorten this arc and to aid the observer

in keeping his gaze perfectly fixed, a second screen was placed before

and very close to the pendulum, between it and the observer. This

screen was stationary. In it was a hole six inches long and two inches

wide. The top and bottom of this hole were arcs of circles parallel

with the arc in which the pendulum swung. The ends were radii.

The screen was so placed with reference to the observer that the moving

image would pass directly across the middle of the opening, appearing

from behind one side and disappearing behind the other. In the centre

of the opening, directly in front of the place occupied by the moving

image when the pendulum was at rest, were two luminous fixation-points,

one above the other, below the path of the moving light. In order

to measure apparent spatial differences between the phases of the

stimulation, two wires were stretched vertically across the opening

in the stationary screen. These wires could be moved nearer together

or farther apart. Thus by measuring the apparent distances in space

between the different parts of the moving figure a measure could be

had of their temporal differences in coming into consciousness. The

luminous image moved, during the time it was visible, at a velocity of

about one and a quarter feet per second. Since the observer sat about

ten feet from the instrument, this would be at an angular velocity of

about seven degrees per second. In one experiment a higher and a lower

velocity were also employed.

It was of course very easy to change the figures and vary them widely

in form, color, and intensity. Most of those employed, however, were

rather small, subtending an angular distance of not more than one

degree. Since the whole opening did not subtend an angle of more than

three degrees or so, nearly all the phases of the stimulation occurred

at the fovea.

We noticed that the form of the stimulating images themselves seemed

to suffer modification as the light swung by, not only because of the

train of after-images which dragged behind them over the retina, but

in other ways as well. For instance, a circular image (Plate III, Fig.

1) appeared crescent-shaped, and its forward edge possessed greater

curvature than the segment of the circle which produced it. It was

longer also from horn to horn than the diameter of the generating

circle, and a faint haze surrounded the points extending outward and

backward until lost in the blackness of the background. Von Kries

remarks that a circular moving image appears cylindrical in form with

a concave edge behind. By using a little higher speed we observed this

phenomenon. At first we thought the crescent-shaped image to be due

merely to an intensely black after-process, which Bidwell describes

as following the positive image of a bright white light. This, taking

place before the circular disc of light had gone forward a distance

equal to its own diameter, would overlap the bright image from behind

and a crescent-shaped figure would result, but the increase in width

and convexity of the stimulating image as well as the laterally

trailing clouds of light remained to be explained, and as this could

not be done in terms of anything which might happen to the back of the

image, another explanation had to be sought. In order to determine

the effect of the form of the figure used as a source of light on the

form of the apparent image, several differently shaped figures were

employed. In place of the original circle, an oblong pointed at both

ends was tried (Plate III, Fig. 2). The front of this figure appeared

very convex indeed, while the ends, which, owing to the shape of the

figure, were very much less effective as a stimulating source, trailed

far behind the centre.

A crescent-shaped figure (Plate III, Fig. 4) gave rise to a very pretty

phenomenon. When it moved toward its concave side, it appeared very

much less concave on that side than the real figure, but when it moved

the other way, toward its convex side, it seemed very much more curved

than it was in reality.[23]

[Illustration: PLATE III.]

No. 3, a simple oblong figure, appeared curved like the others, almost

as perfect a crescent as any of them.

The idea occurred to me that perhaps all these modifications in the

curvature of the figures could be explained if we assumed two things:

First: that there is a spreading of excitation from one portion of the

retina to another. Each point will therefore be stimulated not only by

the light falling directly upon it, but it will also derive a certain

reënforcement of its stimulation from the points surrounding it. Thus

a point lying toward the centre of one of these figures would be more

favorably situated for receiving reënforcement than one located toward

the periphery, where there are few neighboring points, and those lying

mostly in one direction, namely, toward the centre.

This may be represented diagramatically, as in the illustration

(Plate IV, Fig. 10), where the horizontal coördinates represent the

spatial dimensions of an oblong image and the vertical coördinates

the intensity of the excitation due to direct stimulation and its

reënforcement by surrounding points at various portions of the

figure.[24] Secondly I assumed that the stimulation at one part of the

figure being thus rendered more intense, that part would appear in

consciousness more quickly than the others and cause a modification

in the form of the figure.[25] For example, in the case of the oblong

figure, the light would be rendered most intense at the centre and

less and less intense toward the ends, for the points in the centre of

the figure will have their intensity increased by nervous excitation

spreading to them from points lying toward the ends. Those toward the

ends will be reënforced by light coming only from toward the centre.

Thus the intensity of the centre of the figure will be increased, and

as the figure moves across before the observer, the centre, appearing

first in consciousness, would likewise appear foremost in space, the

points near the centre a little later and so on, until finally, the

ends being the last to appear, the whole front of the figure would take

the form of a convex curve, after the manner in which it was observed.

The back of the figure also appears curved, probably because of the

fact that the front of the negative after-image, which closely follows

it, is of the same shape as the front of the positive image, as was

shown in the case of the circular figure.[26]

It is of course a well-known psychological fact that a light of

greater intensity will take less time in coming into consciousness

than one of less intensity. In this case, however, it was necessary to

find some way of showing such differences between lights which were

very little different in intensity. For one is practically unable to

see any difference in intensity between the parts of a stationary

image. So unless it could be shown that a difference in intensity

between two sources of illumination, so small as to be imperceptible

to the observer, will nevertheless make its presence known by the

appearance of the brighter light in consciousness before the other,

the explanation which I have suggested for the curvature of the images

would have to be abandoned.

The following experiments do show, as I believe, that of two sources

of light not perceptibly different in intensity, the brighter will

appear in consciousness before the other, and that in the case of these

figures the curvature of the image is due to a heightened intensity of

the light in the centre through reënforcement of the excitation there

present by stimulation spreading from the ends.

EXPERIMENT I

In the first of these experiments three dots of about three sixteenths

of an inch were placed in a vertical row about three eighths of an inch

apart (Plate IV, Fig. 1). No change was then observed in the form of

the figure. The row of dots swung across the opening in a perfectly

vertical line one directly above the other (Plate IV, Fig. 2). They

were presumably too far apart for irradiation to take place between

them. When, however, another dot was interposed between each end dot

and the centre dot (Plate IV, Fig. 3), so that the excitement could

extend from one dot to the next, the front of the line of dots no

longer appeared vertical, but decidedly convex, the centre dot being

perhaps three eighths of an inch before the dots on the ends (Plate IV,

Fig. 4).

[Illustration: PLATE IV.]

Absolutely the only difference between the two cases was that in the

one, irradiation presumably could not occur, while in the other it

conceivably could.

EXPERIMENT II

In the second of these experiments the curvature of a line of dots was

observed and measured. Then the centre dots were slightly darkened

(Plate IV, Fig. 5) by shading lightly with a lead pencil the ground

glass which travelled with the pendulum and held in place the card

from which the dots were cut, until the front of the image lost its

curvature and appeared vertical (Plate IV, Fig. 6). The pendulum was

then stopped and the row of dots observed closely, in order to see

whether the dots in the centre were perceptibly of less intensity than

those on the ends. No perceptible difference was found.

EXPERIMENT III

All the dots were covered, except the shaded central and the two

unshaded end dots, in order that no irradiation might take place

between them (Plate IV, Fig. 7). The pendulum was again set in motion,

and the centre dot, instead of remaining co-linear with the dots on the

ends, appeared considerably behind them (Plate IV, Fig. 3). This would

show that irradiation must heighten the intensity of the excitation in

the centre of the figure--for the two cases just mentioned are alike in

every respect except that in the first (Fig. 6), where the dots were

near enough together so that irradiation might occur between them, the

intensity of the centre dot, which was objectively fainter than the

end dots, was heightened enough by this induced excitation to appear

in consciousness as soon as the two end dots, which were objectively

of greater intensity; whereas in the second case (Fig. 7), where the

dots were too far apart for irradiation to take place between them,

the centre dot, being objectively of less intensity than the end dots,

appeared behind them.

These experiments show that of two sources of light very little

different in intensity the brighter will appear in consciousness

before the other. Other things being equal, the difference in

intensity may even be so small as to be imperceptible by direct

comparison; it is able nevertheless to make its presence known by

the order in which the lights appear. Exner made some experiments in

1868 to determine the time necessary for the perception of lights of

different intensity. He used, however, stationary images of brief

duration and tried to eliminate the effects of the after-image

by flooding the visual field with light. This method has its

disadvantages. It is incapable of measuring the minute temporal

differences in latent perception of sources of light very slightly

different in intensity.

While my method does not give the absolute time taken by any one light

to enter consciousness, it is a very much more delicate method than

Exner's for measuring _differences_ in time of latent perception of

sources of light very close to one another in intensity. It would be

a very easy matter, having found the time of latent perception for a

light of standard intensity, to determine by this method the time of

lights of greater or less intensity.

These experiments also show that when irradiation is absent, the

curvature of the images is absent; when irradiation is presumably

present, curvature is present. For I find, not only in these, but also

in a number of other experiments, that under all conditions in which

the presence of irradiation is to be expected, the form of the images

tends to be modified in precisely the manner that the assumption of its

presence would lead one to anticipate. In all cases where irradiation

is presumably absent, the contour of the front of the moving figure

depends entirely on the amount of light proceeding from its different

parts.

It is next in order to say something of the physiological causes of the

phenomena we have been considering.

It is probable from what has been observed that in the case of the

curved figures we are dealing with a form of visual irradiation which

is due to the spreading of neural excitation over or through the layers

of the retina. It is also evident from the close connection between

irradiation and intensity that it must be of such a kind that the

excitation produced in one part of the retina may communicate itself

readily to another part. We have also seen in the case of the moving

line of dots that the several dots could remain distinct from one

another and yet could reënforce each other by means of communicated

excitation. It must also be a very rapid form of irradiation, for the

curvature of the figures does not increase very much during the time

they are visible.

I think that the demands made by these different facts are best met

by assuming that the spread of the nervous excitation which gives the

reënforcement takes place in one of the interconnecting layers of nerve

cells and fibres underlying the rods and cones. The line of dots which

appeared curved and yet perfectly distinct from one another could

very well communicate excitation to one another along these fibrils,

and the intensity of one part be raised by the excitation of the

near-lying parts. The fact that the dots remain distinct would not be

contradictory. For in that case very near-lying parts might communicate

excitation to one another without arousing to any very great activity

the nerves that lead to the brain from the small unstimulated portions

which lie between them. In this manner the intensity of the centre dots

could be heightened enough to make the row appear convex, without any

merging into one another on the part of the several dots. The fact that

the dots do not fuse shows that the curvature is not due merely to a

forward-spreading of the excitation in the retina. However, there is

always a certain amount of light visible between the dots, with all the

colors. This is especially noticeable with green light.

The fact that the elements of the retina form a kind of concatenated

series from without inwards, a number of rods and cones corresponding

to but one ganglion cell, furnishes a further bit of evidence in

support of the explanation just advocated, since the irradiated

excitation would tend to be "drained off" through the group of ganglion

cells corresponding to the most highly stimulated portions and leave

the intervening spaces comparatively free from centrally proceeding

excitation. Thus also the individual dots in the five-dot figures may

appear entirely distinct from one another and yet the centre ones be

reënforced enough by irradiation to appear in consciousness in advance

of the others.

SUBSIDIARY EXPERIMENTS

A number of other observations were made which present various

exemplifications of the principles we have considered.

EXPERIMENT IV

An oblong figure, all its parts objectively of the same intensity,

had its ends slightly darkened. When this was done the curvature had

increased from twelve sixteenths to fourteen sixteenths of an inch.

The pendulum was stopped, and a very slight difference was perceived

between the ends and the centre of the figure. This difference in

intensity was greater than in the dot experiment, when the image had

been darkened enough in the centre to make it appear vertical, because

in this case, when the ends were darkened the centre would still be

reënforced by irradiation from a considerable space which intervened

between the shading and the centre.

EXPERIMENT V

The centre of the oblong figure was considerably darkened so as to

counteract the effect of induction. By properly varying the amount

of shading, one may make the front of the figure appear less convex,

vertical, or even concave. This shows perfectly the effect of

differences in intensity upon the curvature of the figure, but does not

show so neatly as the similar experiments performed with the dots, the

influence of the presence or absence of irradiation upon the intensity

of the centre of the figure and so upon the curvature.

The illustration shows a case where the centre was too much darkened.

[Illustration]

The two ends were comparatively free from shading. In each end-part

irradiation took place. The points lying toward the centres of these

ends received reënforcement, both from points lying toward the centre

of the figure and from the extreme ends, and so the centres of the ends

of the image were considerably brighter than either the extreme ends

of the figure itself, or the sides of the end-parts toward the heavily

shaded centre of the figure. Accordingly each end appeared convex for a

short distance. The whole figure, however, being considerably brighter

at the two ends than at the centre, on account of the heavy shading,

the ends appeared in consciousness first and the centre afterwards, so

that the figure as a whole seemed concave.

EXPERIMENT VI

An oblong figure was shaded rather heavily at one end, gradually

becoming lighter toward the other, while about a third of the figure

was free from shading. The shaded end always seemed to lag behind. The

extreme front of the figure was at a point a little distance from the

other end, before the shaded portion began. So that the front of the

whole figure appeared, not like a segment of a circle, but like part of

an oval with the bulge toward the brighter end.

Beyond the ends of all these images faint clouds of light were seen, as

has been mentioned before, extending outward and backward, gradually

decreasing in intensity, until lost in the surrounding blackness of the

background.

Charpentier's bands, sometimes more and sometimes less in number, were

observable in all of my figures and with all colors. Very often they

appeared to be parallel to the forefront of the image, or even of a

slightly greater degree of curvature.

EXPERIMENT VII

It is a well-known fact that a rotating color-disc, having colors which

just fuse at a certain intensity, will show flicker at a slightly less

intensity.

A color-disc was set in motion and the speed found where the colors

were on the point of fusing. A piece of black cardboard, with a hole

about an inch in diameter, was held close to the screen.

Around the periphery of the hole flickering appeared, while at the

centre there was fusion. (The cardboard was held very close to the

disc, so that there would be no shadows on the disc near its edges.)

This fusion at the centre of the disc is probably due to the fact that

the centre of the field is of slightly greater intensity than the

edges, owing to irradiation. This difference in intensity makes the

difference between the fusion at the centre and the slight flicker seen

at the periphery.

Karl Marbe in a recent article mentions the difference in fusion

between a point in the centre of the disc and a point near its border,

and he thinks the increase of flickering in the latter is due to

some influence on the part of the moving edge which separates the

different parts of the disc. It would seem more probable from this

last experiment that the fusion at the centre of the field of view

was due to reënforcement of intensity by irradiation, and that the

flicker about the periphery of the field was due to the lack of such

reënforcement.

EXPERIMENT VIII

Three large dots were used and the centre one covered with tissue

paper. The two end dots then appeared ahead of the centre dots. They

were larger than the centre dot, due to irradiation over their borders.

But this increase in size did not account for their position ahead in

space. The centres of all the dots were not co-linear, but the middle

dot was behind the others, thus, of course, showing the greater time

necessary for the perception of the less luminous object.

EXPERIMENT IX

This was exactly similar to the preceding, except that the intensities

of the various dots were reversed. The end dots were covered with

tissue paper, instead of the centre one. Then the centre dot appeared

first and the end dots after it.

EXPERIMENT X

Professor Hess finds that an image which, compared to those we

used, was very long, subtending an angular distance of about thirty

degrees, and which extends entirely across the fovea and overlaps the

surrounding parts of the retina will appear curved backwards at the

fovea, owing to the longer time of latent perception of the fovea and

the macula. The accompanying illustration shows a modification of one

of Hess's figures, in which the presence of this phenomenon and that

of the convex image are both shown. The two phenomena were observed

when a two-inch image was observed at a distance of about fourteen

inches. The intensity of the light was that of an eight-candle-power

lamp with three pieces of ground glass in front of it. (Very many of

Hess's intensities are too great to give convex images.) Thus the image

would be about 12° in height. About 5/12 of the figure would then fall

on the macula and fovea and appear curved backwards in relation to the

ends. The ends where they fell on the extra foveal parts of the retina

appeared convex in front and concave at the rear as any small image

of the right intensity does which falls on a homogeneous part of the

retina.

[Illustration: Figure observed with centre curved backward at the

fovea, and ends curved forward owing to irradiation.]

EXPERIMENT XI

Charpentier, Bidwell, and others have made the observation that if

a small source of light be exposed for a brief interval, excitation

will proceed out in all directions over the retina, but if the light

be exposed for a slightly longer period, the excitation will contract

again and the light appear nearly its proper size and in its proper

location at the stimulated portion of the retina. Using variously

shaped figures we obtained analogous results, and the additional fact

appeared that the outgoing excitation proceeds from the borders of the

figures and that its form is somewhat determined by the form of the

figure. An oblong image appeared vaguely elliptical, a diamond-shaped

figure in the form of a more pointed ellipse, etc. These images were

exposed for only a small fraction of a second, by means of a shutter.

As the exposure grew longer the true form of the figures came out more

and more clearly. There thus seems to be a general spreading of the

stimulation in all directions over the retina from the borders of the

images. Then, upon a slightly longer duration of the stimulus, this

very rapid irradiation of excitation contracts and the irradiation

becomes confined within the borders of the stimulated portion and

affects the intensity of the different portions of the image. With

strong intensities and certain colors it is, however, never wholly

confined to the stimulated portion even of moving images. Charpentier

speaks of "clouds of light accompanying his figures." With green light

these clouds are especially noticeable. His "palm branch" phenomenon is

a good instance of the irradiation of stimulation.

Besides these experiments which I have just described, several

phenomena of a like sort were observed in connection with other

experiments which were being performed in the laboratory at the same

time. Dr. Holt was experimenting with a bright circular spot of light

about one half inch in diameter, surrounded by a very faint ring about

one half inch wide. When the whole image was moved about, the spot

would seem to go back and forth across the less intense part so that

the whole image looked like a jelly-fish swimming about in the water.

When the figure was allowed to remain stationary for a few moments it

would resume its natural shape. Otherwise the bright part would seem to

advance faster than the rest, sometimes even overlapping the border.

This phenomenon was due to the fact that a bright light requires less

time in coming into consciousness than a less intense one, and is, of

course, the same in principle as those which were performed with dots

when the bright dot moved ahead of the rest.

Another one of these phenomena occurred when an isosceles triangle

was moved in a direction parallel to its base. The side toward which

it moved appeared curved forward, with the apex bent backward. Toward

the bottom, where there was the best chance for irradiation to have

its effect, appeared the most advanced portion of the figure, while

the bottom corner, although objectively the most advanced part of the

figure, appeared rounded off and somewhat behind the part just above.

A narrow, vertical image with a large bulge behind the central part

appeared with a large portion of this bulge in advance of the centre of

the figure.

All these experiments show that a more intense object is, other things

being equal, always located ahead of other objects co-linear with it.

And I assume irradiation to account for the priority in localization

of parts of the figure which are not objectively of greater intensity

than others, but whose position makes them subject to reënforcement.

The localization itself may be a function of more central organs, and

not directly a question of the coming into consciousness more quickly

of a more intense stimulation, although that seems to be the simplest

explanation, but in any case priority of localization varies directly

with the degree of intensity.

If the light is not bright enough to produce much irradiation the image

will lose its curvature. If the light is too bright, although there

may be a maximum of irradiation aroused and the absolute difference in

intensity between the ends and centre of the image be at its greatest,

yet this difference may not be great enough in proportion to the

absolute intensity of the light to make the centre of the image appear

in advance of the rest.

The curvature also varies with the angle subtended by the image and the

portion of the retina upon which the image falls. If the image were too

long, although all the processes which produce curvature be present,

yet the front of the image would still appear vertical, because of the

fact that each point in this long line would not derive reënforcement

sensibly greater than that of the neighboring points. The best one

could expect would be that these long figures should have their ends

rounded off, which is usually the case. Most of the images which

Professor Hess used in his experiments were too long to appear curved.

All the images whose curvature we measured did not subtend an angle

greater than 1° 10´, and were all seen on the fovea.

An image which subtends an angle of more than about 2° will hardly

appear curved when it passes over the fovea.

We were sometimes able to see the curvature reversed. This happened in

my own case about once in a hundred times, usually when my eyes were

fatigued by the repeated passing of the moving light back and forth

over the same portion of the retina. With other observers it occurred

more often.

Slight vertical differences in fixation would cause the central part

of the path taken by the moving light to become more fatigued than the

edges and so to respond more slowly to the stimulation and reverse

the curvature. It may be that some brain process which has to do with

the apperception of the form and movement of visual objects becomes

fatigued or does not always function properly, and so the curvature

of the image may sometimes appear reversed. At any rate the more

usual cases are those in which the convexity is present. The others,

owing to the number of factors involved, and the vast majority of the

opposite cases, may be regarded as due to temporary defects in the

psycho-physical mechanism, which when properly working would give the

more usual result.

QUANTITATIVE EXPERIMENTS

The object of the following experiments was to measure the amount

of curvature produced by differing degrees of intensity of light at

different speeds. An oblong figure was employed one fourth inch wide

and two inches long. As has been mentioned, two vertical wires were

stretched across the path in which the light moved. As the light swung

by, it was attempted to get the wires at such a distance from one

another that when one appeared tangent to the curve at the front of

the figure the other would seem to cross the image at the point of

intersection of the curve with the rest of the figure, as indicated in

the diagram. (Plate IV, Fig. 9.)

The distance between the wires was then read off on a scale. Thus one

was able to obtain a measure of the curvature of the figure when it was

moving at different speeds and illuminated by different intensities of

light, and to compare the observations of different subjects. The mean

error in this work is surprisingly little, considering the difficulties

in making the judgment as the light passed rapidly by the wires.

Usually the moving light had to be observed several times before the

curvature of the front of the moving image could be measured exactly.

It would be perfectly obvious that the front was considerably curved,

but it would often be wholly impossible to tell just how much it was

curved, until the pendulum had swung back and forth four or five times.

Fatigue and darkness adaptation modify the judgments considerably. If

one's eyes were partially adapted to darkness some little difficulty

was experienced in seeing clearly the curvature of the image. Fatigue

comes on very rapidly indeed. Usually it was impossible to get more

than four judgments without resting, and often only two could be made.

It was sometimes impossible to measure the curvature at the exact point

when the light passed under the cross-wires, so the curvature had to be

observed carefully and compared with the distance between the wires,

and a judgment made when the wires were not superimposed upon the

image. With each intensity of light two judgments were taken, one when

the cross-wires had to be brought nearer together, the other when they

had to be moved farther apart. Several series of measurements were made

by different observers, and the results averaged up and compared.

The following curves and tables give the different observations for the

nine different intensities of white light,[27] and the three speeds

which were used. In the case of the high speed the light moved across

the opening in the screen placed before the pendulum at a velocity of

about 1.5 ft. per sec. The middle speed was about 1.27 ft. per sec. and

the low speed about .917 feet per sec. In all cases an oblong image was

used, 1/4 inch wide and 2 inches long. The numerals on the left of the

plotted curves give the apparent curvature of the image in sixteenths

of an inch, and were obtained by measuring the distance between the

cross-wires when this distance measured the apparent curvature of the

image in the way described above. The figures at the bottom designate

the different intensities of light which were used. Number one is the

greatest intensity, number nine the least; the others those in between.

_High Speed._ This curve shows very well indeed what seems to be

typical of the relations between the intensity of the moving light

and the apparent curvature of the front edge of the image. With the

lowest degrees of intensity the amount of the curvature is very little.

Sometimes it was difficult to measure it at all. The light was so

faint and the speed so rapid that probably very little reënforcement

or irradiation took place, although what did occur would show its

presence most prominently, since, on account of the high speed at

which the pendulum moved, any part of the image which should come

into consciousness ahead of the rest, even by a very little time,

would appear considerably in advance of the rest of the image in

space. Of course a certain amount of time would be required for the

stimulus to spread itself over the retina, since it has to overcome

a certain amount of resistance in the nerve-layers, and if this time

were not given, the curvature of the resulting image would be of course

decreased. As the light brightened, however, the curvature increased

rapidly, until finally, when the intensity of the light neared its

highest point, the curvature ceased becoming greater, and finally

decreased. The mean error in eight judgments taken by two people for

each intensity of light was about .099 in.

[Illustration: High Speed]

[Illustration: Middle Speed]

[Illustration: Low Speed]

The measurements with the middle speed were very similar. The curvature

with the lowest intensity of light was somewhat greater than when this

same light moved with the highest speed. The maximum point of curvature

was reached with a light of less intensity, and the curvature was less.

When yet higher intensities were used, the curve decreased rapidly. The

amount of curvature was also much less with the brightest light than

with the higher speed. The following table shows the judgments of three

observers for this speed:

MIDDLE SPEED

Intensities. 1 2 3 4 5 6 7 8 9

First Subject. 8 10 9 11 10 9 9 7 8

10 11 13 13 10 11 10 9 8

10 10 11 11 9 8 8 7 7

10 11 11 14 10 12 8 9 9

10 11 10 11 9 9 7 10 7

11 11 11 13 10 10 9 10 7

Second Subject. 10 9 11 11 12 8 11 7 8

12 14 13 14 15 14 10 9 9

10 14 13 13 12 11 11 10 9

11 14 13 13 13 12 12 10 9

13 11 13 14 12 12 10 9 9

13 12 13 14 12 12 11 11 9

Third Subject. 7 10 9 13 10 9 9 7 8

8 12 12 13 12 10 10 8 7

7 11 10 10 11 10 10 8 8

9 11 13 11 12 10 11 8 8

9 11 11 10 10 9 10 9 7

9 11 12 12 11 10 10 8 8

Average. 9-15/16 11-1/3 11-1/2 12-5/18 11-1/9 10-1/3 9-7/8 8-5/8 8-1/9

Mean Error, .075 in.

The low-speed measurements show the same general tendencies except

that the curvature is smaller with this speed when the faintest lights

were used than with any of the others. The maximum curvature is also

less and occurs with a more intense light than with the middle speed.

These modifications offer no special difficulties. Since the light

moves slowly, although the centre of the image, which is reënforced

by induced excitation from the ends, does appear in consciousness in

time ahead of the rest of the image, yet it does not appear so far in

advance of the rest of the figure in space as it would if the light

moved with a higher speed. While the same difference in brightness

between the centre and the ends of the image should make one part

appear in consciousness just as far ahead of the rest in time with

this speed as with any other, yet since the speed is slow it would not

appear to be so far ahead in space. The fact that the maximum amount of

apparent curvature is less would also be explained in the same manner.

When the high and middle speeds were used the results were surprisingly

consistent and the variations between the observers not very great.

With the low speed the individual differences are very much more

prominent. Uncertainties and variations between observers and between

different observations of the same observer became greater and greater

as the intensity of the light decreased. One seemed to be approaching

the lower limit of induction, below which, even if the spreading of

light stimuli through the retina took place at all, it was to such a

slight extent that it made no very marked difference in the appearance

of the moving image. Individual differences are very great in this

respect. For instance, my own average measurement was 15/64 in. of

curvature for the image produced when a light of the lowest intensity

moved at the lowest speed. Mr. Vaughan's measurements averaged 30/64

in., a measurement of just twice as much for the same light at the same

speed.

So far there has been given only a general view of what happens when an

oblong moving image appears convexly curved. It may be well to consider

the different causes which determine a certain curvature of the image

and see how they are related.

As we have seen, the curvature is a function of the difference in

intensity of various excitations between the centre and the ends of the

retinal area excited. This difference is modified both by the objective

intensity of the light and by the speed at which the light moves. Its

efficiency to produce curvature is also modified by both these factors,

since it requires a certain small amount of time for the irradiation to

take place. If this time is not given by the too rapid passage of the

image over a certain part of the retina, the difference in intensity

will be lessened and the curvature therefore be decreased. On the other

hand, if the figure moves too slowly, although this difference in

intensity may be as great as possible for the brightness of the light

which is acting, yet the curvature may be lessened on account of the

fact that, although the centre of the image does appear ahead of the

ends in time, yet it does not appear so far ahead of the ends of the

image in space as it would if the same difference in intensity were

present and the image moved more rapidly.

It will be remembered that the intensity of the centre of the figure

owes its increase to reënforcement by excitation irradiating from the

surrounding points. It seems only reasonable to suppose that this added

intensity due to irradiation does not increase without limit, or with

exactly the required ratio to produce a curvature of the front of the

image which becomes continuously greater as the intensity of the light

increases, indefinitely.

If this be so, then, at a certain brightness, the difference in

intensity between the ends and the centre of the image will have

reached a maximum, and a further increase in brightness of the light

will not serve to increase the apparent curvature of the image, but

rather to decrease it.

COLOR IRRADIATION

The color of the image has a decided influence upon the amount of

perceived curvature, independently of the intensity.

The following experiments were performed with lights of different

colors, in order to investigate the relations between the kinds and

amounts of irradiation of the different colors by comparing the amounts

of the curvatures obtained. We encountered a good deal of difficulty in

fixing upon a proper method of comparison between the different colors.

Finally it was decided to use such intensities of light as would give

a maximum amount of curvature with each of the four primary colors,

to measure this amount in each case, and also to measure the amount

obtained when the intensity of the light was greater and less than that

required to give the maximum.

It was found that very different objective intensities of light were

required to give a maximum amount of curvature with the different

colors. The colored images were obtained by placing colored pieces of

glass in a frame which stood before the source of light. The intensity

of the light could be regulated by interposing or taking away pieces

of ground glass which rested in the frame between the light and the

colored glass.

The red glass gave a nearly saturated color, but its place in the

spectrum was rather nearer the orange than I could have wished. It

was a thick piece of glass and absorbed a great deal of light. A

32-candle-power light with four pieces of ground glass in front of it

gave a maximum curve for most observers.

The yellow gave a very well-saturated color with light from the

incandescent lamps which we used. The glass was thinner and absorbed

less light than the red. A 32-candle-power lamp with three pieces of

ground glass usually gave the maximum.

Two 32-candle-power lamps and one of 24-candle-power were required with

the green.

The green glass was not quite so saturated in color as the red or

yellow. It was a slightly yellowish green. Red and yellow rays were

visible through it to some extent when it was examined through the

spectroscope. It absorbed somewhat less light than the red and

decidedly more than the yellow. The maximum curvature was obtained when

the source of light was screened with four pieces of ground glass.

The blue glass was a bluish violet, very heavy, and absorbed a great

deal of light; it allowed many red and violet rays to pass through. It

was necessary to use with this glass two 32-candle-power lamps and one

100-candle-power. When the combined light of these lamps was reduced by

interposing three thicknesses of ground glass, the maximum curvature

was observed. The light which then appeared, however, seemed of greater

intensity than any other which gave a maximum.

The curvature of the white light was measured again in order to compare

it with the colored lights. This was necessary, since the work was done

with a different set of subjects and the former work showed individual

variations. An 8-candle-power light was used as before. This, reduced

by four pieces of ground glass, gave the maximum in most cases.

The following curves and tables show the average of the observations of

four subjects. In the table the figures under the columns numbered 1

and 2 represent the amount of curvature perceived when the intensity of

light was greater than that required to give a maximum under 4 and 5,

when the light was not strong enough to produce a maximum of curvature.

The columns numbered 3 represent the greatest amount of curvature

perceptible with each color.

The curves shown in the diagram represent these measurements plotted

out.

TABLE

Intensities. 1 2 3 4 5

Red. 13.50 15.20 16.85 14.06 13.46

Yellow. 13.90 15.46 18.00 16.40 15.85

Green. 15.66 18.00 19.86 18.32 18.00

Blue. 13.00 14.15 16.85 15.50 14.09

Average for all

the colors. 14.00 15.70 17.90 15.90 15.35

The measurements were made in the same way as before, and are given in

sixteenths of an inch.

In the diagram the abscissas represent the different intensities, the

ordinates the amount of the curvature. To avoid confusion, the curve of

the average of all the colors is left out of this diagram.

[Illustration]

It will be noticed in these records that the different colors give very

different measurements of curvature. Green gives by far the largest,

being greater than any of the others at every point. Since the process

of obtaining the curvature was the same with all the colors, these

differences in curvature can only be due to inherent differences in

the processes which give the sensations of the different colors.

It cannot be due simply to one sort of intensity process, the same

for all the colors, otherwise the curvature of all the colors would

be the same. At the same time the curvature of the image is due to

differences in intensity of excitation between one part of the image

and another. There must be, therefore, a retinal excitation in some

respects different for each color, capable of its different degrees

of intensity. Of course these individual differences would have a

decidedly limited range, for, as every one knows, if the intensity of

a color be increased sufficiently its saturation vanishes and white

appears in its place, while if the intensity be decreased without

limit, black appears. It may be that different degrees of excitation in

the different processes have different rates of time in coming into

consciousness, so that an equal degree of difference in excitation

between the ends and centre of the green image and the ends and centre

of the red image would give decidedly different amounts of curvature,

if it took a longer time after the centre of the green image had

appeared in consciousness for the ends to appear than it did in the

case of the red.

The time-differences might be greater with the same differences in

intensities of excitation with one color and another. Or it may be

that the excitation spreads in a different manner with each one of the

colors, and therefore gives differing degrees of reënforcement with the

different colors, and thus produces different amounts of curvature.

It is noticeable also that the amounts of curvature are related to one

another in a peculiar way. Green has the greatest amount of curvature,

yellow the next. Red is greater than blue with the higher intensities,

they are equal at the maximum, and blue is greater than red when the

lower intensities are used.

When a spectrum showing a fair degree of saturation is observed, it is

seen that the point of greatest brightness lies in the yellows. As the

intensity is heightened, this point moves toward the red end, and as it

is lowered, it moves toward the blue.

It will be seen that the relation between the different amounts of

curvature for the different colors is the same as that between the

different degrees of apparent brightness when the intensity of the

colors in the spectrum is decreased. It is not that of the extreme case

of the phenomenon of Purkinje, but when the point of brightness has

moved from the yellow into the yellowish greens or decidedly to the

right of the place it occupies in the normal spectrum. In that case

yellow would be the color second in brightness. In our measurements

the amounts of curvature obtained from yellow images were next in size

to those of green. The red and the violet-blue which we used would

therefore be about equal. It is a noteworthy fact, however, that when

the intensities of light (1) and (2) are too great to give a maximum of

curvature the amount of curvature obtained with the red is greater than

that of the blue, while with the intensities which are too small (4)

and (5) to give a maximum the blue curve is greater than the red.

As yet it has not been possible for me to find an interpretation of

these facts which would seem to meet all the requirements, and I

should not wish to offer any explanation at present. The question

of the possible connection of this phenomenon with Purkinje's is

probably important for any explanation, though it is possible that the

arrangement of the curves is merely a coincidence, yet this hardly

seems likely, and it would seem as if an explanation of the connection

would involve an attempt at explanation of Purkinje's phenomenon, and

lead at once into the most doubtful problems of the theory of visual

sensations.

It is also noticed that the series of numbers obtained when the

amounts of curvature of the different colored images, at the different

intensities given in the foregoing table, are averaged up, and the

curve of the average of all colors is thus obtained, that this average

curve is very like that obtained for the white light. These curves and

the series of numbers which they represent are here given.

[Illustration]

Average for all colors. 14.00 15.70 17.90 15.90 15.35

Curve for white light. 11.50 15.00 17.80 15.75 14.25

It will be noticed, however, that the curve for the white light, while

nearly equal to that of the average for the colored lights at the

maximum point, nevertheless falls considerably below it at each end.

This may possibly be due to the fact that with white light it was only

necessary to use an 8-candle-power lamp as a source of light, so that

when pieces of ground glass were interposed in order to reduce the

intensity of this light, very much greater reduction would occur with

this comparatively weak source than would take place with an objective

source of light of far greater brilliancy, as was the case with the

colored lights. Hence there would be a greater difference in absolute

intensity between intensities 1 and 3 with the white light than between

intensities 1 and 3 with any of the colored lights, or that represented

by their average. Thus the falling of the curve of the white light

at each end may possibly be due to the fact that there is a greater

difference in intensity represented by these parts of the curve in the

case of the white light than is represented by the analogous portions

of the curve of the average of the colored lights.

It will be remembered that these measurements were obtained when

the image was upon the fovea, so that the white obtained was "cone

white," and not due in any way to the functioning of the rods. It is

interesting to note that the curve of the white is very near that of

the average curve of all the colors, though I should hesitate to draw

the conclusion from this that "cone white" is due to a mixture or

fusion of all the excitations corresponding to the different colors.

In regard, however, to relations of the amounts of curvature of the

images, there are several further considerations which ought to be

noted. In the first place all three measurements were made when the

images were entirely on the fovea. In the fovea there are no rods, so,

whatever the connection of these facts with Purkinje's phenomenon, it

is one which has to do with the functions of the cones alone.

Professor Hess, in his experiments upon totally color-blind subjects,

found that exactly the same oscillatory processes in the course of the

stimulation occurred with them as with normal subjects. He also found

that the difference in the time of latent perception between the foveal

and extra-foveal parts was the same for one set of subjects as for the

other. The sole difference seemed to be in the one fact of not being

able to perceive colors. From these facts it does not look as if the

difference between seeing colors and color-blindness were by any means

always due to the absence of cones in the color-blind eye. It may of

course be true that an eye which is deficient in cones or which has

a lesion of the fovea would have poor color perception. But it seems

also true that an eye which, in so far as the rods and cones and their

purely retinal processes were concerned, seems to be normal in every

way, except perhaps that somewhat different intensities were required

to give the same reactions (which might be explained by different

central processes), may nevertheless belong to a person who is totally

color-blind or totally unable to perceive colors with that eye.

If this should prove true, the cones would still be regarded as the end

organs of color perception, but the cones would only give sensations

of color when functioning in conjunction with some other more central

process. The usual cases of color-blindness would be attributable, not

to any deficiency in the cones or any other retinal process, but to a

defect in this more central process, which, working in conjunction with

the cones, gives us our sensations of color.

The usual views of the functions of the rods would not be affected by

these considerations. They would continue to be regarded as end organs

whose main business it is to deal with weak stimulations and to notice

movement in objects whose images fall upon the periphery of the retina.

But the main difference would be that all cases of partial

color-blindness and most cases of total color-blindness would be

explained by lesions in the brain rather than abnormalities of retinal

structure.

VARIOUS FORMS OF IRRADIATION

The endeavor to explain these phenomena of moving images which we

have been considering and an examination of the literature of the

subject have led me to conclude that there are five distinct types of

irradiation. These are:

1. Irradiation α. The very rapid spreading of the nervous excitation

over the retina, which extends far beyond the borders of the image

and which occurs immediately upon stimulation. It is most distinctly

observed with stationary sources of illumination of the briefest

duration perceptible. This kind of irradiation has been discussed at

length by Charpentier and Bidwell.

2. Irradiation β. As the apparent form of the moving image becomes

distinctly perceptible, such irradiation takes place within the

confines of the stimulated portion of the retina, so as to make the

excitation present at favorably situated localities more intense than

that of other places. The portions which are so situated as to receive

this reënforcement are the first to enter consciousness. The various

phenomena discussed earlier in this paper furnish examples of this

process, as well as the phenomenon of the curved image.

3. Irradiation γ. After, and in part during, the rise and development

of the reënforcing irradiation, emanations of nervous excitation of

small intensity proceed from the borders of the stimulated portions

and from the after-images, rapidly extending themselves over the retina

and gradually decreasing in intensity.

4. Irradiation δ. When two fields of different intensities are brought

into juxtaposition, the field having the greater intensity will enlarge

itself at the expense of the other. This constitutes what has been

usually termed irradiation, and is observable with stationary objects.

This enlargement varies with the time during which it is observed, the

absolute intensity of the light employed, and the relative differences

in intensity of the two fields. Its angular extent under determinable

conditions is constant, although it varies considerably from one

observer to another, and with the same observer at different times.

Its physiological explanation is probably similar to that of the

other kinds of irradiation, viz., the spreading of nervous excitation

over or through the layers of the retina, although various factors of

accommodation, dispersion, achromatism, astigmatism, etc., enter in

and modify the totality of the phenomenon. It will be noticed that

reënforcement occurs in this kind of irradiation as well as in certain

of the other forms. The sides of the dark fields upon which this

form of irradiation shows itself appear curved inward at the centre,

apparently showing the presence of a greater excitation in the lighter

fields next to the centre of the darker ones.

5. Irradiation ε. When a luminous object has been observed for a long

time (from thirty seconds to several minutes), the whole surrounding

field will be flooded by a faint haze of light, which within certain

limits increases in intensity the longer the stimulation is present.

This phase has many characteristics of the first and most rapid kind of

irradiation, and possibly represents a discontinuance of functioning,

through fatigue of certain nervous mechanisms which prevent the

spreading, or inhibit the perception, of this irradiatory excitation

after the form of the object is distinguished clearly. It is probably

largely due to such a mechanism that we are enabled to perceive as

clearly and sharply as we do the outlines of objects which differ

greatly in intensity from their backgrounds.

W. McDougall has developed a theory of inhibition[28] which he uses

to explain the more usual kinds of irradiation. This explanation

harmonizes very well with the results of my own experiments and helps

to explain all the kinds of irradiation we have distinguished. Briefly

stated the theory of inhibition is this: there is a transference of

nervous excitation or energy through the nerves and from one neurone to

another. This living nervous energy he calls neurin. The place where

it crosses from one neurone to another he calls the synapse.

Of course these conceptions are not to be taken too literally. They

seem to be rather, if they are to be of any value at all, a convenient

way of handling certain neurological processes of which at present we

know very little, but whose grosser modes of action are comprehended

more easily by the use of such terms as "resistance," "neurin," etc. It

is in this manner that I wish to be understood in the use I have made

of Dr. McDougall's valuable contributions to the methodology of the

subject.

Neurin is generated when a stimulus is applied to the afferent nerves.

When a strong stimulus is applied, neurin is generated rapidly, and

discharges across the synapse to the efferent neurone in a series of

very rapid discharges like the multiple discharge of a Leyden jar.

When the stimulus is weak the discharges take place more slowly.

Consciousness occurs at the time of the discharges and occurs in

pulses. When these pulses occur in very rapid succession we experience

a continuous sensation, when the discharges take place at a lower rate

we are conscious of a pulsative sensation, as for instance, in the

visual phenomenon of Charpentier's bands.

Continuance of stimulation continues to produce neurin, but the

multiple discharges caused by the incoming neurin cause fatigue in

the synapses, and the neurin seeks new paths of discharge through

unfatigued synapses.

The resistance of the synapses is first lowered by the incoming neurin,

then raised again through fatigue. When the resistance is first lowered

upon application of the stimulus, the neurin which might go through

other channels of discharge is "drained off" through the synapses which

have their resistance thus lowered, then as the resistance is again

raised through fatigue, it again seeks discharge through synapses which

are unfatigued.

Applying these conceptions to the different kinds of irradiation we

have distinguished, we can bring them all under one category. One

might remark in passing that, in so far as our purposes are concerned,

it makes very little difference whether we regard consciousness as

occurring upon the crossing of neurin from one neurone to another, or

upon the charging and discharging of a cortical cell, so long as the

conditions already referred to are maintained, viz., first, a lowering

of resistance as the incoming nervous excitation finds its way through

the cell or across the synapse, and then the gradual rise of resistance

and its conduction into new channels by fatigue of the synapse, or

exhaustion of the cell and a consequent turning of the excitation

through fresh cells across fresh synapses before its passage into the

efferent nerves.

When a light stimulation falls upon the retina, during the first one

hundredth or one fiftieth of a second the nervous excitation of neurin

will spread about generally through the retina for a considerable

distance from the point immediately excited. Thus by means of the

fibres of the retina faint excitations will go to the brain from all

these different points, so that one will perceive a faint cloud of

light, similar to that described under the first kind of irradiation.

Moreover, since the portion of the retina directly stimulated by the

light will have the most intense stimulation, this part will come to

consciousness somewhat more quickly than the outlying parts, so that

the cloud of light will first seem to spread outward from its source,

and then, as the resistance in the synapses is lowered through the more

intense stimulation of the part of the retina upon which the light

directly falls, the outrunning excitation will be "drained off" from

these portions of the retina outside of the borders of the image, and

the halo or cloud of light will appear to contract again. This was

observed by Charpentier and Bidwell, and in our own experiments.

Moreover, in case the synapses corresponding to the portions of

the retina indirectly stimulated should have themselves periods of

discharge and periods of charging, we might expect to see dark rings

upon this halo, this was also first observed by Charpentier and Bidwell.

Secondly, as the resistance is lowered in the central organs

corresponding to the end organs of the retina upon which the

stimulation falls, the image tends to assume its true form, but

irradiation has been, and probably still is, present through the layers

of the retina, so that certain favorably located portions of the image

secure reënforcement by means of this irradiation, in the manner

described, and these portions appear in consciousness sooner than

the others. This reënforcement, in the case of the travelling oblong

image, will make it appear convex. Moreover, since the resistance of

the synapses corresponding to the centre of the oblong images will be

less than those corresponding to the ends, there will be a certain

tendency to "drain off" the stimulation from the rest of the image, a

sort of reënforcement of the reënforcement, which will also help in

making the image appear curved. Of course all the conditions which we

found to modify the curvature of the images will still hold good, these

conceptions being used only to describe the course of events which

causes the image to appear convex. Thus a very weak or a very intense

or a very long or an excessively short image will not appear curved,

owing to a lack of difference in intensity between the ends and the

centre great enough to produce perceptible curvature.

As to the third kind of irradiation, that which proceeds from the ends

of the moving image over the unstimulated portions of the retina,

and which has the appearance of long streamers of light extending

outward and backward from the moving image, this may be regarded as

being in certain respects a form of the first and very rapid kind

of excitation. It may well be that all the outrunning excitation

which occurs immediately upon stimulation does not find its way to

the central organs through those nerve-paths which correspond to the

directly stimulated portions of the retina, even after the form of

the image may be very clearly determined, but that some excitation

proceeds outward from one retinal element to another, arousing fainter

and fainter excitation as it proceeds. This being the case, we should

expect to find these streamers of light from the ends of the image

extending outward and backward over the retina. Of course the faster

the image moved and the more intense it was, the longer then would be

these streamers. For if the image moved very fast, very much less of

the excitation would be "drained off" through the directly stimulated

portion, and thus more of the excitation would be left behind, so to

speak, by the image when it moved along rapidly, and this would appear

to drag farther and farther behind. Of course these streamers being

curved backward would appear more curved the faster the image moved,

and if the pulsative processes occurred with these stimulations which

occur in the course of other retinal stimulations, we should have

Charpentier's "palm-branch" phenomenon.

The fourth kind of irradiation which we have defined is of course

the best-known form, and is that which has been the most discussed

by the many writers on the subject. It will be remembered that this

form appears in stationary objects which have been observed for some

little time (from four to ten seconds), and consists in the apparent

enlargement of a more intensely illuminated portion at the expense of

a less illuminated one. This enlargement occurs after all trace of

the first kind of irradiation has vanished, and of course no trace of

the third kind comes in, since the object is stationary. The course

of events may then be somewhat as follows. In the first perception

of the object we have the wide-spreading irradiation described. Then

way is made through the synapses corresponding to the stimulated

portion of the retina, and the wide-spreading irradiation is drained

off through these open channels, so that the image contracts again to

its proper size. But at the same time it is not likely that there

will not be a slight irradiatory enlargement of the borders of the

image. For irradiation is present within the confines of the image.

This is shown not only in the case of moving images, but also in the

fact that the edges of the less intensely illuminated portions of the

field are curved inward, this being most probably due to the fact that

the centres of the contiguous luminous portions are reënforced by

irradiation proceeding from the direction of both the ends.

Not all of the excitation proceeds to the brain from the directly

stimulated portions of the image merely, but a little irradiates

over the borders and causes an apparent enlargement of the brighter

field. It has also been shown by Plateau and others that the amount

of irradiation increases both with the intensity of the stimulation

and with the time during which it acts. Of course, as to the intensity

there is no question. As to the time-element, it may be that the

excitation at the border spreads rather slowly outward after the

previous contraction of the image to its proper dimensions, which takes

place within a very short time after stimulation, until a sort of

balance is reached between the tendency of the image to enlarge itself

through irradiation and the tendency for this irradiatory excitation

to be drained off through the nerves corresponding to the stimulated

portion of the retina, after which no further apparent enlargement

takes place.

In some of our experiments with dots we found that after a dot of the

proper intensity of illumination had been steadily gazed at for some

time the centre would appear dark. This seems to be due to the fact

that the centre of such an image was reënforced by irradiation, so

that the nervous mechanism corresponding to it became fatigued more

quickly and the stimulation at the centre no longer gave such intense

sensations as the rest of the figure, but appeared darker.

Passing to the fifth and last variety of irradiation, this seems due

to fatigue in the inhibiting apparatus which reduced the spread of the

first kind of irradiation. Following out the scheme we have applied,

it would seem as if the channels which were first opened by the direct

stimulation became blocked through fatigue, and, therefore, the

excitation produced in the retina were forced to seek new paths through

to the brain by means of the nerves which proceed from the unstimulated

portions of the retina. Thus if the resistance through fatigue occurs

slowly, the excitation which spreads may increase in intensity and in

extent. So, as the resistance increased, a portion corresponding to the

directly stimulated portion and its slight irradiatory enlargement of

the borders would be surrounded by a cloud of light growing in size and

intensity.

Of course the limiting case would be when the external cloud of light

attained as great or even greater intensity as the stimulated portion,

but such a case would probably be impossible to realize because of

other conditions which would prevent.

It may be that this fifth variety is caused partly at least by a

cortical spreading of the excitation. But it seems to me more likely,

in view of the fact that we could find no irradiatory enlargement of

the binocular portions of stereoscopic images and for a number of other

reasons, that the induction is retinal in character and that after

the resistance through fatigue has arisen in the central organs the

stimulation spreads out over the retina to the unstimulated portions

of the field and proceeds from thence to the brain. This seems more

probable than that the stimulation continues to be confined merely

to the stimulated portion of the retina, but seeks passage from one

portion to another of the brain through fresh neurones which branch

only from those nerve-tracts which proceed from the directly stimulated

portions of the retina.

To conclude; we have seen that there are various forms of irradiation

which take place during the perception of stationary and moving sources

of illumination.

That there are certain modifications in the form of a moving image

which are probably due to one of these processes.

Concerning color irradiation it was found that the curvature of the

images varied with the color of the light, so that a figure illuminated

by a colored light of one intensity would not have the same curvature

as one illuminated by a light of the same intensity but of another

color. Green gives the greatest curvature, yellow the next, red and

blue about the same. In other words the differences in curvature of the

images follow the order of the brightness of the colors in a spectrum

the intensity of which is much reduced.

From a consideration of these phenomena we were led to discuss the

functions of the rods and cones in the retina of the eye, and the

suggestion was made that differences in color-vision were due to

central rather than retinal processes, and that in many cases of

partial or total color-blindness the retina would be found normal and

the defect in vision due to a lesion in some more central structure.

The various forms of visual irradiation which have been described

by a number of different writers we found to be all forms of one

rather simple process. Resistance, removal of resistance upon further

stimulation, and recurrence of resistance through fatigue in some part

of the optic tract, together with the spreading of stimulation over the

retina (probably through the molecular layers) from one afferent nerve

to another are assumed as the minimal requirements which are sufficient

to explain the five forms of irradiation which have been considered in

this paper.

FOOTNOTES:

[Footnote 23: Image no. 5 appeared with the concavity in front. In the

centre of the figure appeared a dark grayish splotch of light, very

much darker than the rest of the image. This is due, most probably, to

the presence of Charpentier's phenomenon of recurrent bands. If this

happens in this figure the ends of the recurrent bright images would

overlap while the centres would not, so that the black bands appearing,

as it were, through interstices in the central part of the figure,

would seem like a dark splotch, especially since the outlines of the

bands are vague and hazy. The back end of the figure had the effect of

being vertical or nearly so. This is probably due to the same cause as

that which made the circular figure to appear as it did, namely, the

negative after-image overlapping the positive after-image. The front

of this black image is usually of about the same shape as the front of

the real figure which it follows. If this is so, then, in this case, it

would make the back part of the image pretty nearly vertical.]

[Footnote 24: The intensity of the objective stimulation may be

represented by the line _AB_. If there were no reënforcement of

stimulation the whole figure would be flat on top and of this height.

The difference between _AB_ and _AC_, or _BC_, represents the increase

of intensity due to irradiation at the most favorably situated portion

of the figure. The other portions receive increments proportional to

their location, as indicated in the diagram.]

[Footnote 25: Favorable localization will of course depend largely on

the shape of the figure in which the point is situated. Thus one in the

angle of a triangle or at the horn of a crescent would have much less

reënforcement of excitation than another point, say halfway down the

side.]

[Footnote 26: Bidwell describes this "black process" or "negative

after-image" of a bright, white light as being of a blackness more

intense than the ordinary blackness of an entirely dark room. This is

perfectly true. The black image, however, lasts for a very much longer

time than the recurrent images of the same light. Often this velvety

black band would trail along behind the moving light for the distance

of a foot or more, gradually lightening into the darkness of the

background.]

[Footnote 27: The intensities used with white light are all less than

an eight-candle-power electric lamp placed at about a foot behind the

opening and covered with two pieces of ground glass.]

[Footnote 28: McDougall, 1901, 1903.]

FEELING

THE EXPRESSION OF FEELINGS

BY F. M. URBAN

The material of this paper was obtained by an experimental

investigation which was carried on in the Harvard laboratory from

February, 1904, till June, 1905. The immediate purpose of these

experiments was a study in the expression of the feeling-tone of

simple sense-stimuli. Breathing and circulation were the functions the

changes of which were observed by tracing the curves of thoracal and

of abdominal breathing and the sphygmographic curves simultaneously.

Acoustical, tactual, pain, and smell sensations were studied in this

way, special attention being devoted to the smell and pain sensations.

These stimuli have the advantage that the physiological reactions of

the subject are more uniform than the reactions to other stimuli.

The number of experiments performed in this investigation was large,

although a subject was never experimented on for more than forty

minutes, because the facilities of the laboratory allowed a continuous

experimenting for several hours a day on different subjects. All the

experiments were performed on trained subjects. Only the changes in

the form of the sphygmographic curve will be discussed in this paper.

The results of this observation confirm the observations of previous

investigators in so far as the same changes in the curves were observed

and the introspections of the subject were, on the whole, similar to

those obtained by other observers. It does not seem probable, however,

that a satisfactory discussion of the results can be given on the basis

of merely mechanical measurements of the curves, and it, therefore,

seemed necessary to reconsider the principles of the theory of the

sphygmographic curves.

There are two methods which can be applied to the study of the

psychology of feelings. They are called the method of impression and

the method of expression. The first is a purely psychological method,

while the latter is confined by its definition to the study of the

physiological changes which are the accompaniments of feelings. The

method of expression is never used as a pure method in investigations

which are carried on for psychological purposes, because the

introspections of the subject must be compared with the physiological

results. It therefore has the character of a mixed method. The first

experimental investigations into the psychology of feelings were

started by Fechner, who employed the pure method of impression. At

this time, however, the apparatus for studying the circulation had

been greatly improved and sooner or later these instruments were sure

to be used for a more exact study of the influence of feelings on

circulation. It was to be hoped that the crude observations on the

changes of the heart-beats and of the circulation under the influence

of feelings might be followed up in detail.

Darwin laid stress on the importance of certain bodily accompaniments

of feelings, and he inaugurated the genetic explanation in this

field. But even if the genetic explanation is successfully carried

through, human psychology remains unexplained, and, furthermore, those

emotional expressions which Darwin described form only a part of the

physiological accompaniments which may be observed with the instruments

now in use. The invention or at least the great improvement of these

instruments is due to the investigators in the middle of the last

century, and a more thorough understanding of the delicate changes of

respiration, circulation, and of temperature was not possible before

the construction of these sensitive recorders. It seems that Mosso was

the first to observe these small changes under the influence of mental

activity in general, and feelings in special; in this sense it may

be said that Mosso started the experimental physiology of feelings.

The discovery of the influence of feelings on circulation is very

important, and it is to be appreciated that Mosso saw these slight

changes which escaped an observer like Marey. In the Mémoire offered

to the Academy[29] on March 26, 1860, Marey gives a great number of

circumstances which influence the sphygmographic curve, but feelings

or mental phenomena are not mentioned in this list. It is true that he

speaks in a later publication[30] of the influence of "moral ideas" on

the circulation and makes the hypothesis that these ideas influence the

circulation in the same way as other disturbing influences, _i. e._, by

changing the peripheral resistance. At this time Marey was already in

possession of his sphygmograph, but nothing in this passage indicates

that he saw the influence of feelings on the tracings. On the contrary,

the words "Sans rien livrer à l'hypothèse" seem to indicate that Marey

had no other facts in mind than those commonly known. He certainly did

not follow up his observation, and his statement at this point does not

differ very much from the observations of the old psychologists, that

emotions change certain physiological functions, of which a more or

less complete list is frequently given.[31]

It certainly is a long step from this vague statement to Mosso's

experimental investigations. His new instruments, the plethysmograph,

and the balance, enabled him to study the distribution of the

blood,[32] and he observed the influence of mental phenomena on the

circulation,[33] on the bladder,[34] and on the temperature of the

brain.[35] His work, "La Paura," describes the physiological effects of

emotions somewhat in detail.

The way toward applying the method of expression to the study

of emotions was shown by the results of previous physiological

investigations. Casual observations of the influence of certain

sense-stimuli on respiration and circulation were made by Naumann,

Couty and Charpentier, Thanhoffer, Dogiel, Gley, Mays, Istomanow and

Tarchanoff, Féré, Delabarre, and others.[36] The changes of breathing

seem to be of greater importance, and some writers account breathing

the most delicate physiological index of feelings.[37] It seems,

however, that a satisfactory treatment can be obtained only by direct

comparison of the respiration and circulation, and it now but seldom

occurs that circulation is observed exclusively.

There are three different instruments for observing the circulation:

the plethysmograph, the sphygmomanometer, and the sphygmograph. Each

of these instruments allows one to observe a different feature of the

circulation. The sphygmomanometer records the pressure in the artery;

the plethysmograph records the volume of a certain part of the body;

and the sphygmograph records the movement of a certain part of the

arterial wall. The curves traced with the sphygmograph indicate to a

certain extent the pressure of the blood, and sometimes they are called

curves of blood-pressure to distinguish them from the plethysmographic

curves which are called curves of pulse-volume.

The invention of these instruments is due to physiological

investigations of the pulse. The problem of studying the pulse

by graphic, or at least experimental methods, begins with the

investigations of Hales and Poiseuille. The first great success in

this line was the construction of the "Kymographion" of Ludwig, but

this instrument had the disadvantage that it could be applied only

by scission of an artery. This circumstance, of course, confined the

application of the instrument to the study of the pulse of animals.

After several attempts by Hérisson, Chelius, and others, Vierordt

succeeded in constructing his sphygmograph, by which curves of the

normal human pulse could be obtained. Some years afterwards Marey

constructed his much more sensitive instrument, which was made still

handier by the use of air transmission. Buisson was the first to use

air transmission for sphygmography, but Upham had used it before for

similar purposes. A considerable number of sphygmographs has been

constructed since, and though they may show some improvements in

detail, the technique of the sphygmograph has made no marked progress

since Marey, and his instrument has been found by experimental tests

remarkably exact.

The curves traced with the sphygmograph are extremely variable in shape

and size. In almost every normal curve, however, a steep ascent may be

seen; it is called the up-stroke or percussion stroke, and this part

of the sphygmographic curve has the name of the anacrotic phase. This

line of ascent ends abruptly and within the limits of the usual speed

of the recording drum it goes over into the descent by a sharp angle.

The descending part of the curve is called the catacrotic phase. The

descent is not so abrupt and is not a more or less straight line, but

is interrupted by secondary elevations. The first secondary elevation

is the largest and is called the dicrotic.[38]

These secondary elevations were seen first by Chelius and Vierordt,

and from the beginning they aroused considerable interest. It was

known that sometimes during fever the pulse takes an abnormal form,

where two beats of the pulse, a strong one and a weaker one, may be

felt for every heart-beat (pulsus bis feriens). This form of the pulse

was thought to be entirely abnormal and it was therefore a great

surprise for the first modern investigators to find these secondary

elevations in tracings of the normal pulse curve. The conviction of

the abnormality of the dicrotic pulse form was so firm that Vierordt

always applied his instrument in such a way that it did not trace the

dicrotic elevation, although it was sensitive enough to trace the exact

form of the pulse curve. Marey, however, used his much more delicate

instrument and found the dicrotic elevation in most of the normal

pulse curves.[39] For this reason Marey's sphygmograph met at first

with considerable criticism (Meissner), but the critical examinations

by v. Wittich, Buisson, and Mach showed that the dicrotic elevation

could not be due to an error of the instrument, for so great an error

was out of question, and there no longer remained a doubt as to the

genuine existence of the dicrotic elevation in the normal pulse curve.

The sphygmograph, thus, had revealed two new and surprising features of

the pulse; (1) The ascent and the descent do not take place with equal

rapidity, the ascent being steep, the descent gradual;

(2) the descent is interrupted by secondary elevations. Neither of

these facts could be observed by applying the finger and it seemed

important to explain them. The explanation of the dicrotic promised to

be of special interest, as it was shown that abnormal dicrotism is in

close relation to the normal form of the pulse curve.

This caused considerable interest in the observation of the pulse,

and the sphygmograph was supposed to be of the greatest importance

for medical diagnosis. Burdon Sanderson,[40] Landois, Lorain,[41]

Ozanam,[42] Pfungen,[43] Riegel,[44] Roy and Adami,[45] and others

have studied the sphygmographic curve under abnormal conditions, and

wellnigh all diseases have been studied by these observers with the

sphygmograph. The results were ambiguous and did not seem to justify

the amount of work spent on these observations. The enthusiasm for

the sphygmograph subsided, and it was no longer expected to obtain

a diagnosis, or even, indeed, a prognosis of a disease from mere

inspection of a pulse curve. Later investigators, in fact, confined

their research to the proof of the ambiguity of the sphygmograms,

which could be valuable only in connection with other observations.

It could not be hoped that an explanation of the abnormalities of the

pulse curve would be found before an understanding of the normal form

was attained. It, therefore, seemed necessary to decide between two

theories of the origin of the normal pulse curve, which had opposed

each other almost since the discovery of the existence of the dicrotic

elevation. Both theories chiefly refer to the origin of the dicrotic,

and they agree on this, that the dicrotic elevation is due to a wave

travelling in the blood, but they disagree on the direction in which

this wave is moving. These two theories may be called the theory of the

peripheral, and the theory of the central origin of the dicrotic wave.

The theory of the peripheral origin of the dicrotic wave assumes that

the change of pressure which is indicated by the dicrotic elevation

originates somewhere at the periphery and travels through the arteries

towards the heart.[46] Commonly it is assumed that the dicrotic

originates in the arterioles. This theory has been mentioned first,

because it is the simpler in every respect, though the less probable.

The origin of the dicrotic wave according to this theory is similar to

the origin of the echo.

Buisson was the first who gave an explanation of the dicrotic elevation

by assuming a central origin of this wave. His theory was adopted by

Marey, who stated it in this way. The action of the heart causes the

blood to be pumped into the aorta with considerable strength. The blood

leaves the aorta by its inertia and expands the arterial system. In

the arterioles it finds an obstacle and being reflected it flows back

to the aorta. But there it finds the semilunar valves closed and a new

wave is produced by reflection. This wave has an effect similar to the

first, and this reflection of waves lasts until the valves are thrown

open again. The existence of several secondary waves is explained by

the great velocity with which the blood travels through the arterial

system.[47]

This theory is open to many objections. First, there is no reason why

the blood wave should not produce a dicrotic elevation when it flows

back to the aorta. Second, the narrow lumen of the arterioles cannot

be an obstacle to the flowing blood, because if an artery splits up

into small branches, the sum of the lumina of the branches is greater

than the lumen of the artery. Lack of space, therefore, cannot be the

cause of the reflection of the pulse wave. Marey, finally, is mistaken

in his conception of the effect of the blood pumped into the aorta by

the action of the left ventricle. He supposes that the entering blood

pushes before it the whole column of blood in the arteries. This view

is refuted by the actual measurements of the velocity of the pulse

wave, because if it were true the pulse would appear at the same moment

in every part of the body.[48]

These are the more obvious of the arguments against Marey's theory.

Other investigators have tried to state a more correct theory of the

central origin of the dicrotic wave. Landois's theory belongs to this

type of improved theories of the central origin. The action of the

left ventricle, according to Landois, causes the primary pulse wave

which travels down the arterial system, until it is extinguished in

the arterioles. The walls of the arteries are expanded by the arriving

blood wave, and, when the valves close, they force the blood onward by

their elasticity. There is a free way to the periphery, but the blood

pushed towards the heart finds the semilunar valves closed and is

reflected. In this way a new positive wave originates which may produce

in the same way a secondary or tertiary wave.[49]

It seemed necessary first to decide between the theories of the central

and of the peripheral origin of the dicrotic wave. Many investigations

have been carried on for this purpose, and some of them bear witness

to the high ability of the investigators. It is, however, remarkable

that the arguments which have been brought forward in favor of one

hypothesis chiefly consist in reasons why the other hypothesis should

not be accepted. These experiments can be divided into two classes.

The first class comprises all the experiments which study the relation

of the pulse curve to other functions, or its dependence on various

conditions. The above mentioned observations of the pathological

changes of the pulse curve belong to this class. The object of frequent

studies of this type has been the relation of the sphygmographic

curve to the curve of the apex beat. The papers of Otto and Haas,[50]

Garrod,[51] Traube,[52] Rosenstein,[53]

Maurer,[54] Gibson,[55] François Frank,[56] and Edgren[57] deal

with this problem. The curve of intraventricular pressure cannot be

studied in man for obvious reasons, and only in some cases has an

attempt been made to compare the sphygmographic curve with the curve

of intraventricular pressure obtained from animals. One of the most

interesting attempts in this line will be mentioned later.

To the second class belong all those investigations, by which

experimental evidence in favor of one or the other hypothesis has been

collected. The experiments which belong to this class are in so far

more decisive as the conditions of the experiments are better known

and, therefore, easier to interpret. Von Kries proved the existence of

the dicrotic in the femoral artery of an animal after having replaced

the heart by a bag filled with liquid.[58] Grashey[59] and Hoorweg[60]

have demonstrated the existence of secondary waves in models, on which

peripheral reflection was impossible. To the same type of experiments

belong Marey's[61] and Grashey's registration of the waves in elastic

tubes, and Mach's[62] tracings from a mechanical model on which the

resulting movement of two simple components could be registered.

Without giving any physiological theory Mach showed how curves similar

to the pulse curves can be obtained by the registration of a movement,

the mechanical conditions of which are known.

As the results of these investigations, we may state the following

facts as arguments against any hypothesis of the peripheral origin of

the dicrotic elevation.

(1) Automatic registration of the pulse wave shows that the dicrotic

appears sooner in the regions nearer to the heart than in regions

which are more distant. The opposite would be the case if the dicrotic

elevation were due to a wave travelling from the periphery to the heart.

(2) The dicrotic appears at the same time after the primary wave in a

dwarf as in a tall man. This would be impossible if the wave had to

travel so much farther.

(3) Inhalation of amyl nitrite makes the dicrotic almost disappear. The

adherents of the theory of the peripheral origin of the dicrotic wave

explain this fact by supposing that this drug dilates the arterioles

and makes little reflection possible. Their opponents say that the

action of the heart and the resistance of the system are so enfeebled

that the backward flow is slight and gives rise only to a small wave.

(4) If an artery is opened and the blood allowed to spurt on a

revolving drum of white paper a curve is obtained which shows the

dicrotic elevation (the hemautographic curve of Landois). The

resistance of the periphery is totally lacking in this case and the

dicrotic elevation could not appear if it were due to a wave reflected

at the periphery.

(5) The appearance of the dicrotic is not retarded if an elastic tube

is placed between the periphery and the place where the instrument is

adjusted. If the dicrotic were due to a wave reflected at the periphery

it would be retarded because the wave would have to travel a distance

so much greater.

These arguments prove the impossibility of the theory of the peripheral

origin of the dicrotic wave. Also the other hypothesis meets with a

number of serious difficulties, and we mention the following facts

which are arguments not against any special form of this theory, but

against any hypothesis which starts from the assumption that the

dicrotic elevation is due to a wave travelling from the heart to the

periphery.

(1) The descent of the catacrotic phase ought to be a succession of

diminishing waves, but not a slow descent with merely small elevations.

(2) This hypothesis accounts for none of the abnormal pulse forms.

(3) The blood ought to push against the semilunar valves with a

force not less than 1/2 - 2/3 of the force of the contraction of the

ventricle, because this is about the relative height of the first

secondary elevation with regard to the primary wave, which is due to

the contraction of the ventricle.

(4) It does not account for the disappearance of the dicrotic

elevation through lack of elasticity of the arterial wall: for the

dicrotic elevation is most marked in youth, becomes lower in old age,

and disappears in diseases like atheroma and arteriosclerosis, which

impair the elasticity of the arterial wall. Landois's theory overcomes

this theory only apparently, although the dicrotic would be absent, yet

in that case the descent of the primary wave ought to be as steep as

its ascent.

(5) This theory is refuted by the experiment of v. Kries, who proved

the existence of the dicrotic if the heart is replaced by a valveless

bag.

The obvious impossibility of making the theories agree with the facts

does not permit one to accept any of them. All of them are based on the

supposition that the dicrotic elevation is due to a wave travelling in

the blood, and this belief is founded on the following argument: If a

wave travels in the blood the sphygmographic curve shows an elevation;

the dicrotic elevation is an elevation in the sphygmographic curve.

Therefore, the dicrotic elevation is due to a wave travelling in the

blood. This fallacy is responsible for the astonishing fact that the

refutation of one of two apparently contradictory statements does not

prove the other. It is characteristic of the present state of the

problem concerning the origin of the dicrotic elevation, that a modern

writer[63] calls it "inextricably complicated."

The contradiction between the theories of the peripheral and of the

central origin of the dicrotic, however, is only apparent, and neither

may be true, because it might be that this elevation is not due to

a wave which travels in the blood. The experiments of the previous

investigators seem to point in this direction. The disappearance of the

secondary elevations when the arterial wall has lost the properties

of an elastic body, the above-mentioned experiments of v. Kries, and

the observations of Grashey and Marey on the movements of the walls

of an elastic tube indicate clearly that nothing but elasticity is

needed to produce these secondary or dicrotic elevations, for, in the

different experiments, they are produced as well when the heart and

its valves are replaced by a valveless bag as when the function of

the valves is unimpaired; as well with resistance at the periphery as

without, the only condition being that the walls are elastic. This

proves the importance of the elasticity of the arterial wall. The

experiments of the graphic registration of the movements of the walls

of an elastic tube, furthermore, indicate that the conditions of this

experiment are a close imitation of the mechanical conditions which

prevail in the arteries. It may be expected that the analysis of the

conditions of the experiment will give an insight into the origin of

the sphygmographic curves, because the tracings which Grashey and Marey

took from the walls of a rubber tube resemble closely the tracings of

the human pulse. This experiment, first, proves that the form of the

curve depends merely on physical conditions. The movement of a point

of the wall of the tube depends on the following four factors: (1) The

elasticity of the wall; (2) the incompressibility of the liquid; (3)

the form of the original wave, _i. e._, the way in which the liquid

is pumped into the tube; (4) the rate of outflow. If the process of

pressing liquid into the tube is repeated regularly, a stationary form

of movement will be obtained eventually; the amount of outflow for one

interval is constant in this case. This means that eventually a state

is attained where the same quantity of liquid which is pumped into the

tube at one end flows out from the tube at the other. The physiological

bearing of this result is that the turgor of an artery does not change

without a cause. Such a change would be indicated by the going up or

down of the base-line of the tracing.

The first two factors are, in physiology, studied with relative

ease. The elastic qualities of the arteries have been studied since

Poiseuille and John Hunter by Wertheim, Zwardemaaker, Marey, and

others, and they are more or less well known. The physical properties

of the blood are very nearly those of an incompressible liquid, and

this is certainly true for the small pressure to which the blood is

exposed in the arteries.

As to the initial form of the wave which the action of the left

ventricle produces in the arterial system, we get a hint from the

experiments of Grashey, v. Kries, and Marey, where the sudden

compression of a bag furnished the initial shock.[64] These changes of

pressure can be represented by a curve like that in Fig. 1.

So long as the contraction of the left ventricle lasts and the valves

are open, the action of the heart produces a certain pressure in the

aorta, but the influence of the intraventricular pressure is zero when

the valves are closed. The second phase of the curve Fig. 1, where the

pressure is zero, certainly gives the influence of the intraventricular

pressure during the diastole, because there is no communication between

the ventricle and the arterial system when the valves are closed. The

question is whether the rest of the curve can represent the changes of

the intraventricular pressure when the valves are open.

[Illustration: Fig. 1. Changes of pressure produced in a bag by sudden

compression.]

[Illustration: Fig 2. Decreasing amount of liquid in a tube when the

outflow is uniform.]

The first curves of intraventricular pressure were traced by Chauveau

and Marey. These experiments were made on a horse, and they have been

repeated since it was discovered that they can be performed also on

smaller animals. Besides Chauveau and Marey may be mentioned the names

of Fick, Huerthle, v. Frey, Rolleston, Bayliss and Starling. The curves

obtained by various observers belong to two types; one shows the so

called "plateau," the other does not. Recent experiments have proved

that this difference of results is due to a difference in methods. This

also is suggested by the fact that different curves have been obtained

from animals of the same species. Two methods have been applied lately

for testing these curves of intraventricular pressure. The first

was devised by Bayliss and Starling. It consisted chiefly in the

photographic registration of the movement of the liquid in a manometer

tube. The photographic registration is frictionless, and the mass of

the moving liquid was so small that vibrations by inertia were fairly

excluded for pressures which are not greater than the intraventricular

pressure.[65] The second method was used by Porter. The idea of this

method was to trace only a part of the curve, not the whole. The

writing lever, thus, has in the beginning of the tracing no inertia at

all, and the tracing may be overdrawn but is certainly correct in form

up to the next point of inflexion of the curve.[66] These tests and

the repeated experiments of Chauveau leave no doubt as to the existence

of the plateau.

The varying pressure from the heart which produces the pulse wave may

be described in this way: The pressure suddenly rises to a maximum

and maintains it for a certain time; when the semilunar valves close,

the pressure drops as suddenly as it rose, and remains at zero until

the valves open again. Such a function can be represented by a curve

like Fig. 1, and this is the reason why the complicated action of the

heart can be superseded by the compression of a bag without changing

the mechanical conditions of the problem. Of course it can not be

expected that a schematic curve will show all the details of the real

tracing. It is suggested, however, by Frank[67] that many of the small

irregularities of the curve of intraventricular pressure are due to

vibrations caused by the inertia of the apparatus and that the true

form of the curve of intraventricular pressure is very simple. This

remark is supported by Huerthle,[68] who tested the apparatus of Marey,

Knoll and Grunmach. Marey's tambour was found to be the most exact,

but even this instrument produces deformities in the tracings, though

the general outlines are exact. This would indicate that the schematic

representation of Fig. 1 is a very close imitation of the real form of

the curve of intraventricular pressure, although empirical tracings do

not show right angles and straight lines. It seems, however, that the

undulations of the plateau are genuine, since they are found in the

most reliable tracings, and it may be possible to explain them merely

on the basis of the physical conditions of the experiment.

The fourth factor of importance is the rate of outflow. We may

introduce the following assumption as to the rate of outflow of the

blood through the capillaries: The outflow through the capillaries

is uniform in the short time of one heart-beat. The fact has been

mentioned above that the quantity of outflowing blood must be equal

to the quantity of incoming, for any stationary form of the pulse

movement; this new hypothesis means that the velocity of the outflow

is constant. One might think that this assumption is warranted by the

law of Poiseuille that the amount of outflow through a horizontal

capillary filled with liquid under constant pressure depends on

the fourth power of the radius and on the difference of pressure

at the two ends of the tube, and is inversely proportional to the

constant of friction and to the length of the tube. This law has

been proved mathematically and tested physically only for horizontal

tubes and constant pressure. Neither of these suppositions holds for

the capillaries of the arterial system. The connection between the

hypothesis in question and Poiseuille's law is this. Let us suppose

that an artery splits up in a great number of arterioles which go

off in every direction. The amount of outflow is then a complicated

function, because the law of Poiseuille does not hold for every

direction of the capillaries; but it will be equal to the outflow

through a tube of certain radius and certain direction in the same

time. Our assumption says that the law of Poiseuille holds for this

typical but imaginary tube. The essential point of this hypothesis

is merely the supposition that the outflow of blood through the

capillaries follows α law.[69]

It is possible to show that the graphic registration of a movement

under these four conditions must give curves which correspond to

the pulse curves in every respect. The action of the left ventricle

causes the pulse wave which travels through the arterial system with

considerable velocity. This wave expands the arteries and the whole

system is filled with blood because the wave arrives by its great

velocity at the periphery before the contraction of the ventricle

is finished. The increased pressure forces the blood to enter the

arterioles, through which it passes at a constant rate. When the valves

are closed, the amount of blood decreases uniformly and the volume of

the blood contained in an artery can be represented graphically by a

straight line of more or less steep descent, as is shown in Fig. 2.

Now the walls of an artery have to a high degree the qualities of an

elastic body, and, therefore, they are forced back by elasticity after

being displaced from the position of equilibrium by the shock of the

arriving pulse wave. The movement of a point of the arterial wall,

therefore, results from two components: (1) From the movement which it

would perform if it were merely forced to remain on the surface of the

blood in the artery, and (2) from the movement due to the elasticity of

the arterial wall. Both movements have the same direction, because the

column of blood is enclosed in a cylinder the radius of which decreases

regularly, and the elastic force of the arterial wall is directed

towards the centre. The direction of both forces is in the line of the

radius, and the resulting movement of these two components, therefore,

can be found by simple superposition. Of the first component we know

that it can be represented graphically by a straight line.

An elastic force tends always to bring the body back to the position

of equilibrium; if the distance is not too great, the force is

proportional to the elongation. A physical body is always under the

influence of friction, the acceleration of which is opposite to the

direction of the movement, and therefore diminishes the velocity. The

form of the resulting movement depends on the amount of friction,

and, roughly speaking, we may distinguish two types of elastic

movements:[70] the first type is a periodic movement, the second an

aperiodic. Let us suppose that a body is carried from its position of

equilibrium by a sudden impulse, which transmits a certain velocity to

the body. Friction and elasticity diminish this velocity, and after a

certain time the body attains a maximum elongation, where the velocity

is zero. Then the body returns under the influence of elasticity and

under the retardation of friction. There are two cases possible, either

the elastic force is strong enough to overcome friction and to carry

the body over the position of equilibrium, or it is not strong enough.

In the first case, it is easy to see, the body repeats the same form

of movement on the other side of the position of equilibrium, and

the conditions being constant a vibratory movement results as the

stationary form. In the second case the body approaches the position

of equilibrium asymptotically. The first case may be illustrated by

the vibrations of a magnet needle suspended with little friction, the

second by the movement of a door which is regulated by a well-working

shutter.

These forms of the movement of a body under the influence of elasticity

and friction are illustrated in Fig. 3.

Curve 1 shows a movement where friction is so small that it can be

neglected; it is, of course, a simple sine curve. Curve 2 shows the

effect of friction on vibrations. The period of damped vibrations is

greater than in the frictionless movement, but the amplitudes are

smaller. The amplitudes of a damped vibration decrease constantly and

there is a simple relation between two subsequent amplitudes. The ratio

between them is constant, and, therefore, if one amplitude and this

constant ratio are known, all the other amplitudes can be calculated.

The amplitudes of such a movement decrease as the terms of a geometric

series. The dotted line in Fig. 4 represents the rapidity of this

decrease. It is obvious that the smaller the constant ratio of two

subsequent terms is, the more rapidly will the amplitudes decrease.

This ratio depends on friction, and becomes smaller when friction

becomes greater. A vibration under heavy friction dies out quickly.

Curve 3 shows a movement where friction is too great to allow any

vibrations. The body does not acquire a velocity which can carry it

over the position of equilibrium, but it approaches this position with

ever diminishing velocity.

[Illustration: Figs. 3 and 4]

These are the types of movement which the arterial wall can perform by

its elasticity in consequence of the shock of the arriving pulse wave.

The mechanical nature of the components on which depends the form of

the sphygmographic curve is, therefore, known. The constructions in

Fig. 5 show how the resulting movement can be found.

[Illustration: Fig. 5]

These curves are constructed in this way. The lines _AB_ represent

the time of the interval of one heart-beat. The straight line _EB_

represents the decreasing volume of the artery and the curves on

_AB_ represent the elastic movement of the arterial wall. Both are

synchronous movements, and a line perpendicular to _AB_ gives the

corresponding points. The points of the resulting movement are found

by arithmetical addition of the two ordinates. The results of these

constructions prove that the curves show the dicrotic elevation only

if the elastic force is great enough to make a vibratory movement

possible. Aperiodic movements do not produce this elevation. The

friction is always great for the movement of the walls of an artery,

and there are only the two possibilities, of a vibratory movement which

dies out quickly, and of an aperiodic movement. This accounts for the

fact that the dicrotic elevation may be missing sometimes, and that in

other cases several secondary elevations may be seen, the number of

which, however, is always limited, and their relative height rapidly

diminishing. It may be remarked that the length of the lines _AB_ seems

essential to the form of the resulting curve. Curves I and III differ

very much in the length of the lines _AB_, while the lines _AE_ are

equal and the vibratory movements are only slightly different. The

resultants, nevertheless, seem to differ very much. It is easy to see

that a different speed of the recording drum will have an effect on

the tracings which is similar to that of a change in the length of

the lines _AB_ in the constructions. This is one more reason why mere

inspection of the curves cannot give a satisfactory result.

These constructions show that the sphygmographic curves must show

great variations, since the amount of blood pumped into the system,

the elasticity of the arteries and friction of the surrounding tissues

are subjected very likely not only to individual but also to local and

temporal variations. But under given conditions only a certain form of

the pulse wave is possible, and this form does not change so long as

these conditions do not change. The sphygmograms in Fig. 6 show some of

the typical forms of the pulse curve.

[Illustration: Fig. 6]

No. I shows the influence of high arterial tension, and No. II of low

tension. The first corresponds to No. II in Fig. 5, the second to Nos.

I and III. Nos. IV and V of Fig. 5 show the effect of great friction

and small elasticity. The constructions differ in the form of the

elastic movement; the position of equilibrium is reached with different

velocity in both cases. The resulting movements differ slightly in the

form of the catacrotic phase. Both forms may be seen in No. III of Fig.

6. This sphygmogram was taken from an artery with low tension, and this

form of the sphygmographic curve is well known as characteristic of the

"soft" pulse. If the artery has lost to a large extent the qualities

of an elastic body, and if the outflow is very rapid, the pulse curve

shows nothing but the slight elevation of the travelling wave; No. IV

in Fig. 6 shows a curve of this character.

This theory explains many surprising facts which resisted every attempt

at explanation. The anacrotic part shows a steep ascent, because it

is due to the sudden arrival of the blood wave. It seems that an

interruption in the descent may be seen only in abnormal cases. The

sphygmograms of twelve normal individuals were observed regularly by me

during more than a year without once discovering an anacrotic elevation.

The hemautographic curve of Landois is produced in this way. The form

of this curve depends on the velocity of the escaping jet of blood. The

velocity of the blood flow depends on the resistance of the arterial

system in the sense that the velocity decreases when the resistance

increases. When the arterial wall is in the negative phase of vibration

the lumen of the artery is smaller, and, therefore, the velocity

smaller. This is confirmed by the actual tracings of the velocity of

the circulation by Marey.

It is also obvious that the dicrotic elevation never can arrive before

the primary wave, because the arterial wall cannot perform elastic

vibrations before it is expanded by the impulse of the arriving blood

wave. Neither is it surprising that the "dicrotic wave" seems to travel

in the same direction and with a velocity equal or almost equal to the

velocity of the pulse wave. Such a difference can be produced only by a

difference in the time of the vibrations of the arteries at different

points of the body. The time of one vibration is necessarily very

short, and the length of this interval depends on the circumstances

which determine the elasticity of the arterial wall and the friction.

These conditions may be subjected to local variations. If, therefore,

the time-interval between the primary and the secondary elevation

is measured at two different points (_e. g._, at the carotid and at

the radialis) a difference of time may be found. Starting from the

supposition that the dicrotic elevation is due to a wave travelling in

the blood, one could attribute this difference of time to a velocity of

the "dicrotic wave" which is slightly different from the velocity of

the primary wave. The fact that the dicrotic elevation appears later in

places farther from the heart was interpreted as a proof that the wave

travelled out from the heart. No theory which assumes that the dicrotic

elevation is due to a wave travelling in the blood can give a reason

why two waves of the same form and origin should travel through the

same liquid at different velocities.

At this point a theory must be mentioned, which was brought forward

recently, because it is based on measurements of the velocity of

propagation of the dicrotic wave. This theory is connected with Krehl's

theory of the function of the valves. The blood, according to Krehl,

enters the aorta through a small opening, and expanding in a large

space it produces fluctuations and eddies, which would close the valves

if they were not kept open by the blood which streams through under

high pressure. They must, therefore, close at the moment when the

aortic pressure is equal to the intraventricular pressure. This occurs

shortly after the moment indicated by the beginning of the decline of

the intraventricular pressure curve. Now the second sound of the heart

is heard somewhere in the descending part of the cardiogram[71] and

the measurements of Huerthle[72] have shown that the second sound is

heard 0.02" after the beginning of the descent of the cardiogram. This

seems to indicate that the second sound of the heart is in a temporal

relation to the closure of the valves. Many theories of the origin of

the sounds of the heart agree on this one point that the second sound

is due to a noise in the muscles. It therefore may be supposed that

the second sound is due to the tension of the valves when they close

or shortly afterwards. The problem now would seem to be to find an

elevation in the descending branch of the curve of intraventricular

pressure, or in the tracings of the apex beat, which could be

attributed to the closure of the valves. It was taken for granted that

the curves of intraventricular pressure and those of the apex beat

were identical. In many of these tracings an elevation was found which

may be called "the wave _f_." This elevation is not found in all the

tracings, and its position seems to be rather variable. Edgren[73]

remarks that the wave _f_ was always found near the abscissa no matter

whether the preceding decline of the curve was great or small. In some

of Chauveau's tracings the wave _f_ is missing or indistinct,[74] in

others it is very well marked and approximately in the middle of the

descending branch of the curve.[75]

Edgren made experiments on the temporal relation of the wave _f_ and

of the dicrotic wave, which to avoid misunderstandings he calls the

"wave _f_´." His experiments were made as follows. A sphygmogram from

the carotid and a cardiogram were taken simultaneously, the points

of the writing-levers being in the same vertical line. The wave _f_´

appeared a little after the wave _f_. The length of this interval

could be calculated by measuring the distance between these waves, as

the speed of the drum was known. From this was subtracted the time

of propagation of the dicrotic from the heart to the point where the

instrument was fixed. In this way it was found that the time between

the appearance of the wave _f_ and of the wave _f_´ was equal to

the time of propagation of the dicrotic wave from the heart. Edgren

concluded that the dicrotic wave is in close temporal relation to the

closure of the valves.[76] To this comes the supposition that the wave

_f_´ is due to a change of pressure proceeding from the heart. The wave

_f_´, therefore, could be attributed to the tension of the valves.[77]

Edgren and Tigerstedt are the chief exponents of this theory.

In so far as this theory assumes that the dicrotic elevation is due

to a wave travelling from the heart to the periphery,[78] it is

open to all the arguments against a theory of the central origin

of the dicrotic wave. Against the more special assertion that the

dicrotic elevation is in connection with the closure of the valves,

the following facts must be mentioned. We grant that the tracings

of the apex beat may be directly substituted for the curves of

intraventricular pressure, although this is by no means obvious, since

one tracing gives the form of the pressure changes and the other the

effect of the shock of the heart against the wall of the chest. It is,

furthermore, not proved that the wave _f_ is due to the closure of the

valves and that the waves _f_ and _f_´ correspond to each other so

closely as Edgren's experiments seem to indicate. His measurements of

the length of lines were made with an exactitude of 0.1 mm., but his

computations were carried to the third decimal place of a second. The

third decimal is generally inexact and the second in a large number of

cases. Experimental evidence, furthermore, directly contradicts the

statement that the dicrotic elevation corresponds to the wave _f_.

Fredericq[79] traced pressure curves in the ventricle and in the aorta,

and determined the points of equal pressure in both curves. He thus

found that a point near the beginning of the descent of the curve of

intraventricular pressure corresponds to the dicrotic. His experiments

are rather conclusive against the theory in question, since the wave

_f_ is very well marked in these tracings of Fredericq. The following

facts, however, are fatal for the theory that the closure of the valves

causes the dicrotic elevation: The dicrotic wave disappears in diseases

like atheroma and arteriosclerosis which do not impair the function

of the valves, but affect the elasticity of the arterial wall, and it

is not affected by valvular insufficiency. The independence of the

dicrotic from the function of the valves is conclusively proved by v.

Kries, who found the dicrotic elevation in the femoral artery of an

animal whose heart was replaced by a valveless bag.

All these facts, on the contrary, can be understood easily in the light

of the theory that the sphygmographic curve gives the movements of the

arterial wall, which movement is conditioned by the decreasing amount

of blood in the artery, and the elastic vibrations of the wall around

a variable position of equilibrium. In some cases the conditions of

the problem are rather simple, and admit an analytic treatment, the

results of which fit closely to the experimental facts. This part of

the theory, however, has merely physiological interest, and therefore

is discussed in a separate paper. It may be mentioned at this point

that this theory of normal dicrotism is essentially identical with the

theory of abnormal dicrotism as stated by Galen. He believed that the

second beat of the pulsus bis feriens was due to an elastic vibration

of the arterial wall. "Ex eodem genere sunt dicroti; nam arteria in

occursu quasi repellitur, moxque redit.... Neque enim tum arteria

contrahitur, sed quasi concuteretur, occidit; cuius delapsum a primae

distentionis termino nulla dirimit manifesta quies, ut animadvertitur

in contractione: sed simulatque attolli destitit, recidit atque ita

paulisper vibrata, mox occurrit iterum."[80] Galen, however, is

mistaken in his view, and in his observation that sometimes three or

more pulse-beats may be felt with the finger. No form of the pulse is

known where three or more beats may be felt for every heart-beat, and

the actual tracings exclude the possibility of this observation for

the pulsus bis feriens. The pulsus bis feriens is due to an increase of

the frequency of the heart-beats. If the new pulse wave arrives before

the vibrations of the arterial wall have had time to subside, the new

wave and the already existing vibration may interfere in such a way as

to produce this abnormal pulse form.

The form of a single wave of the sphygmographic curve may be influenced

by changes in the following conditions:

(1) The pulse wave may have an initial form which cannot be represented

by the schematic curve in Fig. 1. This may be due to an irregularity of

the function of the ventricle. The action of the heart has an influence

on the length of the waves, which length is determined by the rapidity

of the heart-beats. This influence has been mentioned before. A change

in the rapidity of the heart-beats has no great influence on the form

of the catacrotic part of the curve so long as the impact of the new

pulse wave does not arrive before the vibrations of the arterial wall

have had time to subside.

(2) Differences of the elasticity of the arterial wall affect

materially the form of the catacrotic part of the sphygmographic curve.

It has also some influence on the height of the curves, because the

amplitude of elastic vibrations depends on the elastic force for a

given force of the shock. The degree of elasticity of the arterial

wall is subjected to individual variations, and it depends in a given

subject on the state of innervation of the wall.

(3) The surrounding tissues have a certain influence, since their

resistance determines the friction opposing the vibration. This

accounts for the fact that merely local conditions, such as a change

of the position of the arm or the adjustment of the instrument, may

change the form of the pulse curve. For instance, if the sphygmogram is

taken from the a. radialis the instrument is placed between the styloid

process of the radius and the tendon of the flexor carpi radialis. In

the neighborhood of this place are two venae comites and a superficial

branch of the median or radial vein. A change in the position of the

arm will have a certain influence on the circulation in the veins, and

influence the turgor of these vessels. Increased turgor increases the

friction, and thus produces the different forms of the tracings.

(4) The changes of the turgor of the artery, moreover, cause a general

rise or lowering of the curve. This symptom is essentially ambiguous

for the turgor of the artery may be changed as well by an increase or

decrease of the amount of blood pumped into the arterial system as by

a decrease or increase of the amount of blood which passes through the

capillaries.

The influences mentioned under (1) may be seen in tracings taken from

cases of cardiac insufficiency, and have merely pathological interest.

All the other influences, however, can be observed in the curves which

are traced for psychological purposes. The changes in the general rise

or fall of the curves are not so very hard to observe,[81] and for the

observation of the rapidity of the heart-beats it is only necessary to

trace a time-curve and count the number of beats or measure the length

of every single beat. Also the changes of the height of the waves can

easily be measured. This has been done conscientiously by several

observers. It is by far harder to see the changes in the form of the

catacrotic branch, and only a few keen observers have seen them. These

changes of the pulse curve under the influence of feelings were proved

as facts by experiments, but their interpretation was doubtful. With

the exception of the rapidity of the heart-beats, which could easily

be observed in some other way, all the symptoms of the influence of

feelings on circulation are ambiguous. A difference in height of the

single waves may be due to a change in the amount of blood which is

pumped into the artery, but it also may be due to a change in the

amplitude of the vibrations of the artery. The form of the catacrotic

part of the sphygmographic curve may be changed by a different state of

innervation of the arterial wall, but it also may be due to an increase

or decrease of the friction of the surrounding tissues. The general

rise or fall of the curve may indicate a change in the amount of blood

which leaves the left ventricle, but it also may indicate a change in

the amount of the capillary outflow.

The problem, nevertheless, is fully determined, and a solution is

suggested by the constructions in Fig. 5. The form of the resulting

movement depends, first, on the length of the line _AB_, secondly, on

the length of the line _AE_, and thirdly, on the nature of the elastic

movement. An elastic movement is determined if three constants are

known, one of which is the amplitude, the second the friction, and the

third the elasticity. Only _AB_ can be measured directly, and there

remain four unknown quantities to be determined. Four measurements

must be sufficient for this purpose. It is obvious, however, that not

any four measurements will do, but a method can be devised by which

it is possible to determine each one of these four quantities. The

problem can be solved in every case provided that the sphygmogram is

trustworthy enough to justify the work. The length _AB_ is proportional

to the time of one heart-beat, and the length of the line _AE_ is

proportional to the amount of blood pumped into the arteries. The

successful analysis of the pulse curves, therefore, shows changes of

the action of the heart and makes it possible to distinguish them from

the changes at the periphery.

Besides the length of the heart-beats there are invariably these

four quantities which must be determined by the analysis of the

pulse curves: Amount of incoming blood, amount of outflowing blood,

elasticity of the artery, and friction of the tissues. These quantities

depend on the action of the heart, the peripheral resistance, and the

state of innervation of the artery. It is not possible to discuss here

the bearing of this theory and of the facts which may be connected with

it, on the different views of the localization and operation of the

centres which control these functions. Anatomical and physiological

evidence, however, leaves no doubt that the function of the heart and

the innervation of the arteries and capillaries _are_ under the control

of nervous centres. It may be supposed, therefore, that changes of

the pulse curve like those due to the influence of feelings are the

effect of the function of these centres. It is to be expected that the

detailed analysis of the pulse curves may give some indications as to

the nature of this influence, for it may be observed how the function

of these centres changes under the influence of mental processes.

A complete analysis of the physiological accompaniments of a

feeling process must give a description of the changes in the

function of the heart and the system, besides a description or at

least enumeration of the other changes which can be observed. By

a number of such investigations material for a general theory of

physiological accompaniments of feelings may be obtained, which

would not be void of interest for the psychology of feelings. Such

a theory must contain the answers to the following questions: (1)

How do the physiological reactions depend on the sense-stimulus? (2)

How many possible circulatory reactions are there? (3) What is the

location and interdependence of the respective physiological centres?

The first question cannot so far be answered in general, but it

will be possible to give a general answer when a greater number of

systematic investigations on the effect of sense-stimuli have been

carried on. Papers like those of Mentz may settle the question for

certain sense-stimuli. From the results which have been obtained so

far it comes out clearly that the reaction does not depend merely

on the nature of the stimulus, but that it depends largely on the

psychical and physiological state of the subject. The answer to the

second question may be given readily, but it seems advisable to give

it in connection with an experimental investigation. It may be said,

nevertheless, that the number of typical reactions is rather limited.

The third problem, by its nature, cannot be definitely answered before

the location of the respective centres is ascertained and their

interdependence explained.

It is, finally, a merit of this theory of the pulse curves that it

shows how the form of this curve may depend on central processes. The

problem of the mysterious influence of mental processes is thus reduced

to the analysis of merely physiological conditions. The theories on the

nature of this influence are so numerous that they may well be called

innumerable, and they vary from accepting a direct influence of ideas

on the circulation to considering the body as a sounding-board which by

every sensation is shaken in all its parts. Each one of these theories

is also a theory of feelings, and a more or less exact description of

these changes has been often taken for a descriptive psychology of

feelings. The example of the sounding-board is taken from one of those

papers which expound the theory that bodily changes follow directly

on the perception, and that our sensation of these facts is the

emotion. Every one of these bodily changes, whatsoever, is perceived,

acutely or obscurely, the moment it occurs. This theory is defended

by the argument that if we try to abstract from consciousness all the

sensations of our bodily symptoms, we find we have nothing left behind.

This argument, which may be found in almost every paper that deals

with this theory, is remarkable, because it sometimes is referred to

processes of every description, and thus comes into contradiction with

psychophysical parallelism which excludes the acceptance of psychical

states which have no physical correlate. This theory, as will have been

noticed, is the theory of feelings expounded by James, Lange, Ribot,

and others. It is widely accepted, and may be found also in books of

popular or semi-popular nature. Two observations must be made against

this view:

First, a perception of a bodily change which is felt in the moment

the change occurs exists only in the theory, every real process

needing a certain time. This point of the theory may be improved by

admitting that the afferent process lasts as long as any other of the

physiological processes of this kind. Either assumption, however, is

contradicted by the experimental evidence supplied by Lehmann that the

physiological changes occur after the beginning of an emotional state.

Secondly, if the theory refers only to those bodily changes which we

know, it certainly is not true, for emotional states are sometimes

observed without it being possible to find with modern instruments any

bodily accompaniments. If the theory refers to bodily changes of every

description, it is certainly true, or, better, it is beyond all attack

because it becomes identical with psychophysical parallelism. In this

general form this theory of feelings is as good as no theory at all,

because it refers to mental states of every description.[82]

This conception of emotional states of mind as perceptions of bodily

sensations would hardly have been promulgated, if the authors had tried

to base it on experiments performed in the laboratory. An emotion

but not the feeling-tone of a simple sensation may be mistaken for

the sum of bodily sensations. It is, furthermore, remarkable that

the promoters of this theory do not make a clear distinction between

sensation and feeling. They introduce an emotional element by calling

the perception of bodily changes a feeling of these changes. Only in

this way do they succeed in building up emotional states of mind out

of elements which are seemingly sensational. This does not succeed if

the word feeling is replaced by the word sensation. The failure of this

theory is due to two facts, first to the starting from a philosophical

doctrine, and second to the lack of a precise distinction between

feeling and sensation. It cannot be doubted after the above discussion

how a definition of this difference may be given which holds for every

empirical investigation.

A sense-stimulus produces a complex of nervous and central processes.

Among these is a certain group of processes which manifest themselves

by changing the innervation of the heart, the blood-vessels, the

lungs, and certain muscles. Another group is formed by those nervous

and central processes which are more or less immediate effects of

the sense-stimulation. The first group of processes is referred

subjectively to an emotional state of mind, and the second to a

cognitive process; the first group of processes is the physiological

accompaniment of feelings, the second that of sensations. The relative

independence of the first group from the second group is warranted

by the fact that the same processes are observed as accompaniments

of ideational processes. A strict limit between these two groups of

processes can be drawn when the central processes are better known,

because to the first group belong all those processes which are found

to be accompaniments as well of sensational as of ideational processes.

In different sensations the emotional process may be more or less

marked, and in others the cognitive process may be prominent, but it

seems that feelings are an invariable accompaniment of the sensation.

This suggests the definition of feelings as psychic processes, the

physiological accompaniment of which are central processes which depend

largely on the state of the organism, and which manifest themselves by

changes in the innervation of the heart, the blood-vessels, the lungs,

and muscles. The impossibility of directly comparing the sensations

of different subjects is recognized, and it is also impossible to

compare feelings, because in either case we are dealing with psychic

processes.

FOOTNOTES:

[Footnote 29: Comptes Rendus, vol. 50, p. 637, 1860.]

[Footnote 30: Comptes Rendus, vol. 53, p. 98, 1861. "Sans rien livrer à

l'hypothèse il est bien certain que des changements dans la circulation

périphérique arrivent souvent sous l'influence d'émotions morales....

En résumé d'après ce qui précède il nous semblerait illogique de faire

une exception pour les actions que les causes morales exercent sur les

battements du cœur, et nous pensons qu'elles doivent agir comme toutes

les autres influences, c'est à dire à la périphérie primitivement."]

[Footnote 31: We quote as an instance Lotze: Medicinische Psychologie,

p. 257, 1852: "Es ist wahr, dass Gefühle sehr lebhafte motorische

Ruckwirkungen äussern; wir sehen die Respiration in Unordnung gerathen,

den Druck der Arterienwandung auf das Blut bei heftigen Schmerzen

zunehmen, Erbrechen auf widrige Geschmackseindrücke, allgemeine

Muskelkrämpfe bei physischen Martern eintreten." All the principal

physiological features of feelings are enumerated here, but one hardly

will give any great credit for priority to Lotze. Such a general

statement, in fact, belongs to the class of easy observations from

which philosophical speculation often starts. G. L. Duprat shows

that the same "observations" underlie the theories of Aristotle,

Hippocrates, and Plato. (Duprat: La psycho-physiologie des passions

dans la philosophie ancienne, Archiv f. Geschichte d. Philosophie, vol.

18 (N. F. 11), pp. 395-412, 1905.)]

[Footnote 32: Application de la balance à l'étude de la circulation du

sang chez l'homme, Archives Italiennes de Biologie, pp. 130-143, 1884.]

[Footnote 33: Ueber den Kreislauf des Blutes im menschlichen Gehirn,

1880.]

[Footnote 34: Mosso et Pellacani: Sur les fonctions de la vessie,

Archives Italiennes de Biologie, vol. 1, pp. 97-127, 1882.]

[Footnote 35: La température du cerveau, Arch. Ital. de Biol., vol. 22,

pp. 264-311.]

[Footnote 36: For the literature, see P. Menz: Die Wirkung akustischer

Sinnesreize auf Puls und Athmung, Phil. Stud., vol. 11, p. 61, 1895.]

[Footnote 37: Meumann und Zoneff: Ueber Begleiterscheinungen

psychischer Vorgänge in Athem und Puls, Phil. Stud., vol. 18, p. 3,

1901; and Wundt: Physiologische Psychologie (5th ed.); vol. 2, p. 298.]

[Footnote 38: It has been pointed out that this terminology, which

is due to a large extent to Landois, presupposes a certain theory of

the origin of the secondary elevations. (Edgren: Cardiographische

und sphygmographische Untersuchungen, Skandinavisches Archiv. f.

Physiologie, vol. 1, p. 92, 1889.) It is not easy to change a

terminology, and the Greek terms, some of which were used by and

before Galen, are so indifferently connotative that they can be kept

without inconvenience. If one were to be rigorous, one would change

the name of the sphygmograph into palmograph, because this instrument

does not serve exclusively for the registration of the abnormal

pulse. It does seem, however, advisable to drop the terms recoil wave

(Rückstosselevation, Landois), and "onde de rebondissement" (Marey),

because they are taken from modern languages and directly suggest a

certain theory with which they are intimately connected.]

[Footnote 39: Recherches sur l'état de la circulation d'après les

caractères du pouls, Journal de Physiologie de l'Homme, vol. 3, p.

249, 1860; and La circulation du sang, p. 264, 1863. "Le dicrotisme du

pouls est un phénomène physiologique, on l'observe presque chez tous

les sujets; seulement il n'est sensible au doigt que dans les cas où

il est extrêmement prononcé." References for previous observations of

the slow descent of the pulse curve are given by Landois, Die Lehre vom

Arterienpuls, p. 36, 1872.]

[Footnote 40: Burdon Sanderson: Handbook of the Sphygmograph, 1867.]

[Footnote 41: Lorain: Études de médecine clinique; Le Pouls, 1870.]

[Footnote 42: Ozanam: La circulation et le pouls, 1886.]

[Footnote 43: Pfungen: Pulscurve der Arterien in Gad's Lexicon der

medicinischen Propaedeutik, vol. 3, pp. 544-642, 1895.]

[Footnote 44: Riegel: Ueber die Bedeutung der Pulsuntersuchung in

Volkmann's Sammlung klinischer Vortraege, Nos. 144, 145, 1878.]

[Footnote 45: Roy and Adami: Heartbeat and Pulsewave, The Practitioner,

vol. 1, pp. 81-94, 161-177, 241-253, 347-361, 412-425, 1890.]

[Footnote 46: Cf. Howell: American Text-book of Physiology, p. 436,

1897. Marey's first explanation of the dicrotic belongs to this type

(Comptes Rendus, vol. 47, p. 826, 22 Nov., 1858.) He supposed that

the dicrotic elevation was due to a wave reflected from the Iliacae

communes. He was led to this theory by the erroneous observation of

Beau, that abnormal dicrotism never occurs in the lower extremities.

Marey's own observations refuted this theory, since they show that the

dicrotic elevation is found also in the sphygmograms of the arteries of

the leg. (Marey, La circulation du sang, p. 274, 1863.)]

[Footnote 47: Marey, La circulation du sang, pp. 271, 272, 1863. "Dans

ces conditions, l'ondée lancée par les ventricules se porte vers la

périphérie, et par suite de la vitesse acquise, abandonne les régions

initiales de l'aorte pour distendre les extrémités du système artériel.

Arrêtée en ce dernier point par l'étroitesse des artères qui lui fait

obstacle, elle reflue vers l'origine de l'aorte; mais cette voie est

fermée par les valvules sygmoïdes. Nouvel obstacle, nouveau reflux, et

par suite nouvelle ondulation (où rebondissement). Ces oscillations

alternatives se produisent jusqu'à ce qu'une nouvelle contraction du

ventricule vienne y mettre fin en produisant une onde nouvelle."]

[Footnote 48: This view was held by Haller, Bichat, and Bourgelat and

goes back to Galen ("Omnes enim clare cernunt, omnes partes arteriarum

eodem distendi tempore," De causis pulsi, book 2, c. 8). The first who

saw that the pulse did not appear at the same time in all the parts of

the body was Josias Weitbrecht, but his observations were neglected

until E. H. Weber actually measured the velocity of the propagation of

the pulse wave. (His famous thesis of 1827,--"Pulsum arteriarum non in

omnibus arteriis simul, sed in arteriis a corde valde remotis serius

quam in corde et in arteriis cordi vicinis fieri.") For the results of

other measurements see Tigerstedt: Physiologie des Kreislaufes, p. 385,

1894. Some use of these measurements is made in the present writer's

L'Analyse des Sphygmogrammes, which is to appear in the Journal de

Physiologie et de Pathologie Générale for May, 1906.]

[Footnote 49: Landois: Human Physiology (English translation), p. 145,

1889, and Die Lehre vom Arterienpuls, p. 188, 1872.]

[Footnote 50: Otto und Haas: Vierteljahrsschrift f. praktische

Heilkunde, vol. 34, p. 41, 1877.]

[Footnote 51: Garrod: Journal of Anatomy and Physiology, vol. 5, pp.

17-27, 1870.]

[Footnote 52: Traube: Gesammelte Beiträge, vol. 3, p. 595, 1878.]

[Footnote 53: Rosenstein: Deutsches Archiv f. klinische Medicin, vol.

23, pp. 75-97, 1879.]

[Footnote 54: Maurer: Deutsches Archiv f. klinische Medicin, vol. 24,

pp. 291-341.]

[Footnote 55: Gibson: Journal of Anatomy and Physiology, vol. 14, pp.

234-240, 1879.]

[Footnote 56: Fr. Frank: Travaux du laboratoire Marey, pp. 301-327,

1877.]

[Footnote 57: I. G. Edgren: Skandinavisches Archiv f. Physiologie, vol.

1, pp. 67-152, 1889.]

[Footnote 58: v. Kries: Studien zur Pulslehre, p. 62, and M. v. Frey,

Die Untersuchung des Pulses, p. 164.]

[Footnote 59: Grashey: Die Wellenbewegung elastischer Röhren, p. 166,

1881.]

[Footnote 60: Hoorweg: Archiv f. d. ges. Physiologie, vol. 46, p. 143,

1890.]

[Footnote 61: Marey, _loc. cit._, pp. 267-271, and Traité de Physique

Biologique (publié par d'Arsonval, Chauveau, Gariel, Marey), vol. 1,

p. 390, 1901; these tracings are reproduced rather frequently; _e.g._,

Pfungen, _loc. cit._, p. 563, and Chapman: Human Physiology (2d ed.),

p. 270, 1899.]

[Footnote 62: E. Mach: Sitzungsberichte der K. Akademie der

Wissenschaften, vol. 47 (2), p. 43, 1863; and in the tables, figs.

48-53.]

[Footnote 63: L. Hill, in Schaefer's Text-book of Physiology, vol. 2,

p. 111, 1902. The same opinion maybe found in Hermann's Lehrbuch der

Physiologie (12th ed.), p. 79, 1900. "Ihre (der dicrotischen Wellen)

Erklärung ist noch nicht widerspruchsfrei gestellt." In the previous

editions different views were given, and this critical doubt may be

regarded as the final outcome of the investigations of almost half a

century.]

[Footnote 64: Sudden compression is the most convenient way of

producing a wave in a liquid which is enclosed in an elastic tube.

It was used already in the first experiments on the propagation of

these waves. (E. H. Weber: Anwendung der Wellenlehre auf die Lehre vom

Kreislaufe des Blutes und insbesondere auf die Pulslehre, Berichte

d. Kgl. Sächsischen Ges. d. Wissenschaften, Math.-Phys. Cl., p. 177,

1850.)]

[Footnote 65: Bayliss and Starling: On the form of the intraventricular

and aortic pressure curves obtained by a new method, Intern.

Monatsschrift f. Anatomie u. Physiologie, vol. 11, pp. 426-435, 1894.]

[Footnote 66: W. T. Porter: A new method for the study of the

intraventricular pressure curve, Journal of Experimental Medicine,

vol. 1, pp. 296-303, 1896. A similar method was used by O. Frank: Ein

experimentelles Hülfsmittel für die Kritik der Kammerdruckkurven,

Zeitschrift f. Biologie, vol. 35, pp. 478-480, 1897.]

[Footnote 67: O. Frank, _loc. cit._, p. 480.]

[Footnote 68: Huerthle: Beiträge zur Hämodynamik, VIII, Zur Kritik des

Lufttransmissionsverfahrens, Arch. f. d. ges. Physiologie, vol 53, pp.

281-331, 1892.]

[Footnote 69: The special assumption on the rate of outflow

is by no means essential for the following theory. Two other

possible assumptions are mentioned in the author's "L'Analyse des

Sphygmogrammes," and others may be found easily. Every one of these

theories is equally probable as long as no experimental evidence can be

brought forward. The assumption that the rate of outflow through the

arterioles is uniform has the merit that it is the simplest and that it

can be deduced from considerations of the average directions of tubes

which split up in "every" direction.]

[Footnote 70: A detailed discussion shows that four different cases are

possible, but this distinction is of minor importance for the purpose

of this paper. The distinction holds that the movement is either

periodic or aperiodic.]

[Footnote 71: Edgren: Kardiographische und sphygmographische

Untersuchungen, Skandinavisches Archiv f. Physiologie, vol. 1, pp.

88-91, 1889; Fredericq: Vergleich der Stoss und Druckcurven der rechten

Herzkammer des Hundes, Centralblatt f. Physiologie, vol. 7, p. 770,

1893; Einthoven und Geluk: Die Registrierung der Herztöne, Archiv f. d.

Ges. Physiologie, vol. 57, p. 631, 1894.]

[Footnote 72: K. Huerthle: Beiträge zur Hämodynamik, Archiv f. d. Ges.

Physiologie, vol. 60, p. 281, 1895.]

[Footnote 73: Edgren: _loc. cit._ p. 87.]

[Footnote 74: A. Chauveau: Inscription électrique des mouvements

valvulaires, Journal de Physiologie et de Pathologie Générale, vol. 1,

p. 388, fig. 4, 1899.]

[Footnote 75: _Ibid._ p. 391, fig. 6 (curve 5); and the same author's

La pulsation cardiaque, in the same Journal, vol. 1, p. 795, fig. 5,

and p. 796, 1899.]

[Footnote 76: Edgren: _loc. cit._ p. 114.]

[Footnote 77: The exposition of this theory may be found in R.

Tigerstedt: Intracardialer Druck und Herzstoss, Ergebnisse der

Physiologie, vol. 1, pp. 258-262, 1902. This theory, equally

remarkable for its logical beauty and for its confirmation by Edgren's

experiments, has not found its way into recently published text-books

of physiology, though Edgren's paper belongs to the most frequently

quoted publications on sphygmography and cardiography.]

[Footnote 78: Tigerstedt: _loc. cit._ p. 261.]

[Footnote 79: Fredericq: La pulsation du cœur chez le chien, no. 5.

La comparaison du tracé du choc du cœur avec celui de la pression

intraventriculaire, Travaux du Laboratoire de Liège, vol. 5, p. 67,

1896.]

[Footnote 80: Galenus: De pulsuum differentiis, lib. 1. c. 16.]

[Footnote 81: The amount of change in the base-line is the chief

difference between the sphygmograms and the plethysmograms. It was

stated recently that for this reason the plethysmograph could not be

used for psychological experiments. An analysis of the mechanical

conditions of these two instruments shows that also the sphygmogram

must show some plethysmographic influences, and the author supplied

experimental evidence for this result.]

[Footnote 82: More recent publications have taken this view. Cohn

speaks of "Organgefühle des Gehirns," approaching Meynert's view on

the causes of pleasure and pain. (P. Cohn: Gemüthserregungen und

Krankheiten, pp. 23 and 50, 1903.) Cohn's book shows clearly that

this theory belongs to the type of philosophical explanations. This

is also suggested by Duprat who remarked the parallelism between the

theories of James, Lange and Ribot, and the theories of certain Greek

philosophers. (Duprat: "La psycho-physiologie des sentiments dans la

philosophie ancienne," Archiv f. Geschichte d. Philosophie, vol. 18

(3), p. 395, 1905.)]

THE MUTUAL INFLUENCE OF FEELINGS

BY JOHN A. H. KEITH

The object of this investigation was to ascertain the mutual influence

of simultaneous stimuli that appealed to different senses with regard

to the _intensity_ of their feeling values. The investigation covers

combinations: (1) of colors and active touches, (2) of colors and

passive touches, (3) of tones and active touches, (4) of tones and

passive touches, (5) of colors and tones.

The basis of appreciation was a numerical scale[83] as follows:

1. Very disagreeable.

2. Disagreeable.

3. Slightly disagreeable.

4. Indifferent.

5. Slightly agreeable.

6. Agreeable.

7. Very agreeable.

The color series began with the one hundred thirty-six colors as put

out by the Milton Bradley Co. This series consists of ninety pure

spectrum colors, ten whites, blacks, and grays, and thirty-six broken

spectrum colors. The colors were exposed at the back of a semicircular

black-lined box for about two seconds. The subject was seated at a

convenient distance, about three and a half feet, from the colors. In

order to have a constant light, all experiments were conducted in a

dark room with an electric light suspended over the subject's head.

The whole series was used for ten times in order to get the range of

judgments. Then twenty-eight colors, covering as fully as possible the

range from 1 to 7, were selected for further experiment in combination.

At the same time a series of thirty-six touches, from velvet to

sandpaper, was being employed as the colors were. From this number

fourteen were finally selected.

Similarly, by using a reed box, with reeds ranging from 128 to 1024

vibrations per second and separated from each other by four vibrations,

from a much larger series twenty-seven tone-combinations were finally

selected.

Moreover, from time to time, each selected series was given alone; and

on the basis of these readings, averaging from thirty to forty, the

"standard" for each stimulus was made. Tables I to III give a brief

description of the stimuli and also the "standards" for each of two

subjects, F. and M.

TABLE I. COLORS

_No. of_ _Description._ _Standard_ _Standard_

_Color._ _for F._ _for M._

1 Violet Red. Tint no. 1 5.90 4.00

2 Red. Tint no. 1 6.00 6.00

3 Red 6.00 5.40

4 Orange Red 5.60 6.20

5 Red Orange 4.20 5.20

6 Yellow Orange. Tint no. 1 3.10 4.50

7 Yellow. Tint no. 1 2.30 5.20

8 Yellow. Shade no. 2 2.00 4.00

9 Green Yellow 2.80 5.60

10 Yellow Green 4.45 6.20

11 Green. Shade no. 1 5.70 4.40

12 Blue Green. Tint no. 1 3.40 6.00

13 Green Blue 5.00 3.50

14 Blue. Shade no. 1 5.40 2.10

15 Blue Violet 5.10 5.00

16 Violet. Tint no. 2 4.20 5.30

17 Violet. Shade no. 2 5.50 3.50

18 Red Violet 5.65 3.70

19 Black 4.00 4.00

20 Green Gray. no. 1 2.20 4.20

21 Green Gray. no. 2 2.00 4.00

22 A-Red. Light 3.70 3.70

23 A-Red. Dark 2.10 2.70

24 A-Orange. Dark 2.00 3.00

25 A-Yellow Orange. Light 3.10 4.30

26 A-Green Yellow. Dark 2.50 4.00

27 A-Blue Green. Medium 2.40 4.30

28 A-Violet. Medium 4.10 4.50

Totals 110.40 124.50

Average 3.94 4.44

In connection with this table it may be noted that the subjects agree

regarding 2, 19, and 22, red tint no. 1, black, and A-red light;

that M. estimates the colors higher than F. in seventeen cases; and

that F. estimates 1, 3, 11, 13, 14, 15, 17, 18, higher than M. does.

These individual differences are probably explicable on grounds

of association; they are not, however, connected with the problem

under consideration here, for we are concerned with the effect of

combinations with other stimuli.

TABLE II. TOUCHES

The various articles were fastened to small pieces of wood and placed

in small cardboard boxes. In active touch, the subjects were allowed

to stroke the object gently twice, always with a contracting movement

of the forefinger of the right hand. In passive touch, the operator

stroked the subject's forefinger with the object, twice as before. The

table explains itself.

_Standards._

_No. of_ _Active._ _Passive._

_Touch._ _Description._ _F._ _M._ _F._ _M._

1 Thick napped velvet 6.90 6.60 7.00 7.00

2 Thin stretched rubber, such as is

used on tambours 5.70 5.40 6.00 6.00

3 Glazed thin cardboard 5.80 5.50 5.50 6.00

4 White silk ribbon--always stroked

with the ribs 5.80 5.70 5.40 5.00

5 Soft, split, rough leather 5.50 5.50 5.00 6.00

6 Smooth polished cork 5.70 5.10 5.40 6.00

7 Glazed tin 5.00 4.50 6.00 6.00

8 Rough, tarred paper 4.30 4.60 4.00 5.00

9 Blue blotting paper 4.50 5.10 4.20 5.00

10 Sand paper no. 1, fine grained 2.20 3.50 2.00 4.00

11 Shot no. 3, set in paraffine 2.70 4.90 3.00 3.50

12 Sandpaper no. 2-1/2, coarse-grained 1.40 2.00 1.50 3.00

13 A coarse, rough, ridged cotton cloth,

always stroked across the ridges 4.00 2.40 4.70 3.50

14 A thin, closely woven white muslin 4.20 4.60 4.20 5.00

Totals 63.70 65.40 63.90 71.00

Average 4.55 4.67 4.56 5.14

TABLE III. TONES

The table of tone-combinations shows that some are simply repetitions

of the same chord in a higher octave, as 1 and 9, 5 and 13, 15 and 14.

The first sixteen are harmonious; so also the twenty-sixth; the others

introduce beats and discords, some of which are agreeable, as 20 and

21, while others are disagreeable, as 19 and 27. Individual differences

appear in this as in the previous series. The totals introduced into

the tables simply go to show that in each series the total judgments

are not widely diverse.

_No of_ _Standards._

_Tones._ _Description._ _F._ _M._

1 256, 320 4.25 3.25

2 256, 384 4.25 3.00

3 256, 320, 384 5.60 3.00

4 320, 384 4.30 3.50

5 256, 512 4.65 5.50

6 320, 512 4.10 5.00

7 384, 512 4.90 5.00

8 512, 640 5.40 5.30

9 512, 768 5.50 5.80

10 640, 768 4.40 5.00

11 640, 1024 4.25 3.40

12 768, 1024 4.80 5.50

13 512, 1024 5.60 5.80

14 512, 640, 768, 1024 6.30 5.90

15 256, 320, 384, 512 6.50 4.00

16 320, 512, 768 5.00 4.70

17 136, 144 2.00 2.50

18 156, 160 3.80 4.00

19 136, 140 2.70 3.50

20 440, 444 6.81 6.00

21 504, 508 6.70 6.40

22 148, 152, 156 1.70 2.50

23 172, 296, 452 3.00 2.50

24 180, 480, 768 3.40 2.50

25 232, 328, 492 3.20 2.50

26 256, 512, 768 5.00 5.50

27 256, 240, 384 2.00 1.70

Totals 120.11 113.25

Average 4.45 4.19

The following tables deal with the combined series.

Table IV shows that the appreciation of the colors was, in general,

lowered slightly by the combinations with the tones; and, also, that

the appreciation of the tones was lowered more than one point by the

combinations with the colors. By referring to Tables I and III, M.'s

average for the colors is 4.44 and for the tones 4.20.

TABLE IV. COLOR-TONE RESULTS. M.

_No. of times color was_ _Total No. of points_

_No. of_ _Not_ _color was_ _Net result_

_Color_ _Raised_ _Lowered_ _Affected_ _Raised_+ _Lowered_- + -

1 3 15 9 3 15 12

2 0 22 5 0 23 23

3 0 27 0 0 32.2 32.2

4 0 27 0 0 20.4 20.4

5 0 27 0 0 8.2 8.2

6 23 4 0 12.5 2 10.5

7 14 13 0 11.2 2.6 8.6

8 6 5 16 6 5 1

9 16 11 0 6.4 6.6 .2

10 1 26 0 .8 20.2 19.4

11 0 27 0 0 36.8 36.8

12 0 23 4 0 23 23

13 2 25 0 1 18.5 17.5

14 9 18 0 8.1 9 .9

15 1 12 15 1 14 13

16 1 26 0 .7 16.8 16.1

17 7 20 0 6.5 12 5.5

18 13 14 0 4.9 10.8 5.9

19 0 0 27 0 0

20 1 26 0 .8 9.2 8.4

21 0 6 21 0 6 6

22 7 20 0 3.1 16 12.9

23 21 6 0 9.3 4.2 5.1

24 12 2 13 17 3 14

25 8 19 0 5 7.7 2.7

26 1 4 22 1 4 3

27 16 11 0 12 3.3 8.7

28 13 14 0 6 10 4

Totals 175 450 132 47.9 271.1

Grand Total (28 × 27) 756. Net lowered 223.2

Average lowering of each color judgment, 223.2/756 = .295

% of judgments of color lowered, 450/756 = 59+

% of judgments of color raised, 175/756 = 23+

% of judgments of color not affected, 132/756 = 17+

_No. of times tone was_ _Total No. of points_

_No. of_ _Not_ _tone was_ _Net result_

_Tone_ _Raised_ _Lowered_ _Affected_ _Raised_+ _Lowered_- + -

1 0 28 0 0 29 29

2 4 9 15 4 9 5

3 2 22 4 2 28 26

4 7 21 0 4.5 17.5 13

5 0 28 0 0 32 32

6 0 24 4 0 35 35

7 0 22 6 0 32 32

8 4 24 0 2.8 11.2 8.4

9 3 25 0 .6 37 36.4

10 0 17 11 0 25 25

11 15 13 0 16 7.2 8.8

12 6 22 0 3 20 17

13 10 18 0 2 22.4 20.4

14 3 25 0 .3 37.5 37.2

15 0 27 1 0 55 55

16 4 24 0 1.2 38.8 37.6

17 2 26 0 1 22 21

18 0 27 1 0 66 66

19 0 28 0 0 56 56

20 1 19 8 1 23 22

21 6 22 0 3.6 13.8 10.2

22 0 28 0 0 37 37

23 1 27 0 .5 33.5 33

24 10 18 0 5 13 8

25 7 21 0 3.5 24.5 21

26 5 23 0 2.5 50.5 48

27 1 27 0 .3 18.9 18.6

Totals 91 615 50 8.8 749.8

Grand Total (27 × 28), 756. Net lowered 741

Average lowering of each tone judgment, .98+

% of judgments of tones lowered, 615/756 = 81+

% of judgments of tones raised, 91/756 = 12+

% of judgments of tones not affected, 50/756 = 6+

TABLE V. COLOR-TONE RESULTS. F.

_No. of times color was_ _No. of points color was_ _Net result_

_No. of_ _Not_

_Color_ _Raised_ _Lowered_ _Affected_ _Raised_ + _Lowered_ - + -

1 9 18 0 10 19.2 9.2

2 0 24 3 0 38 38

3 0 26 1 0 31 31

4 1 26 0 0.4 33.6 33.2

5 9 18 0 7.2 16.6 9.4

6 3 24 0 3.7 12.4 8.7

7 13 14 0 9.1 4.2 4.9

8 9 4 13 9 4 5

9 21 6 0 12.4 5.8 6.6

10 18 9 0 15.90 12 3.9

11 19 8 0 10.7 5.6 5.1

12 9 18 0 7.4 13.2 5.8

13 5 7 15 6 7 1

14 7 20 0 6.2 4 2.2

15 5 22 0 6.5 5.1 1.4

16 1 26 0 .8 17.2 16.4

17 2 25 0 1 13.5 12.5

18 3 24 0 1.35 18.6 17.25

19 0 3 24 0 3 3

20 18 9 0 14.4 2.8 11.6

21 9 0 18 9 0 9

22 5 22 0 4.5 26.2 21.7

23 2 25 0 1.8 5.5 3.7

24 5 7 15 6 7 1

25 1 26 0 .9 28.4 27.5

26 16 11 0 8 5.5 2.5

27 19 8 0 14.4 3.2 11.2

28 7 20 0 6.3 4 2.3

Totals 215 451 90 54.1 250.95

Grand Total 756 Net lowered 196.85

Average lowering of each color judgment, .26+

% of judgments of color lowered, 451/756 = 59.6+

% of judgments of color raised, 215/756 = 28+

% of judgments of color not affected, 90/756 = 11.9+

_No. of times tone was_ _No. of points tone was_ _Net result_

_No. of_ Not

_Tone_ _Raised_ _Lowered_ _Affected_ _Raised_ + _Lowered_- + -

1 6 22 0 3 20.5 17.5

2 2 26 0 1.5 22.5 21

3 2 26 0 .8 24.6 23.8

4 2 26 0 1.4 16.8 15.4

5 4 24 0 1.4 27.6 26.2

6 3 25 0 6.7 26.5 19.8

7 4 24 0 1.4 40.6 39.2

8 1 27 0 .6 32.8 32.2

9 1 27 0 .5 34.5 34

10 8 20 0 5.8 25 19.2

11 3 25 0 2.25 33.25 31

12 4 24 0 .8 38.2 37.4

13 2 26 0 .8 23.6 22.8

14 2 26 0 1.4 25.8 24.4

15 1 27 0 .5 32.5 32

16 0 21 7 0 40 40

17 4 10 14 4 10 6

18 18 10 0 22.6 14 8.6

19 17 11 0 22.1 13.7 8.4

20 6 22 0 4.8 22.6 17.8

21 10 18 0 3 17.6 14.6

22 18 10 0 10.4 7 3.4

23 1 20 7 2 21 19

24 0 28 0 0 20.4 20.4

25 3 25 0 2.4 21 18.6

26 0 22 6 0 39 39

27 1 11 16 1 11 10

Totals 123 583 50 20.4 581.3

Grand Total 756 Net lowered, 560.9

Average lowering of each tone judgment, .742+

% of judgments of tones lowered, 583/756 = 77+

% of judgments of tones raised, 123/756 = 16+

% of judgments of tones not affected, 50/756 = 6+

Table VI. Tone-Active Touch Results. M.

_No. of times tone was_ _No. of points tone was_ _Net result_

_No. of_ _Not_

_Tone_ _Raised_ _Lowered_ _affected_ _Raised_ + _Lowered_ - + -

1 14 0 0 31.5 0 31.5

2 14 0 0 29 0 29

3 14 0 0 30 0 30

4 14 0 0 32 0 32

5 9 5 0 9.5 4.5 5

6 14 0 0 25 0 25

7 14 0 0 22 0 22

8 14 0 0 22.8 0 22.8

9 14 0 0 16.8 0 16.8

10 14 0 0 25 0 25

11 14 0 0 46.8 0 46.8

12 14 0 0 21 0 21

13 14 0 0 13.8 0 13.8

14 13 1 0 13.4 .9 12.5

15 13 0 1 23 0 23

16 14 0 0 24.2 0 24.2

17 14 0 0 25 0 25

18 13 0 1 28 0 28

19 14 0 0 30 0 30

20 13 1 0 13 0 13

21 13 1 0 7.8 0 7.8

22 14 0 0 24 0 24

23 14 0 0 21 0 21

24 14 0 0 42 0 42

25 14 0 0 38 0 38

26 12 2 0 11 2 9

27 13 1 0 22.9 .6 22.3

Totals, 365 11 2 640.5

Grand Total, 378. Net raised, 640.5

Average raising of each tone judgment, 1.69+

% of judgments of tones lowered, 11/378 = .2+

% of judgments of tones raised, 365/378 = 97+

% of judgments of tones not affected, 2/378 = .5+

_No. of times touch was_ _No. of points touch_

_No. of_ _Not_ _was_ _Net result_

_Touch_ _Raised_ _Lowered_ _affected_ _Raised_ + _Lowered_ - + -

1 27 0 0 10.8 0 10.8

2 6 21 0 3.6 12.4 8.8

3 10 17 0 5.8 8.5 3.5

4 6 21 0 2.8 16.7 13.9

5 14 13 0 8 6.5 1.5

6 8 19 0 7.2 6.9 .3

7 16 11 0 11 6.5 4.5

8 22 5 0 13.8 3 10.8

9 7 20 0 6.3 5 1.3

10 26 1 0 23 .5 22.5

11 21 6 0 2.1 5.4 3.3

12 26 0 1 38 0 38

13 27 0 0 48.4 0 48.4

14 23 4 0 14.2 2.4 11.8

Totals 239 138 1 149.9 29.5

Grand Total, 378 Net raised, 120.4

Average raising of each active touch judgment, .31+

% of judgments of active touch lowered, 138/378 = 36+

% of judgments of active touch raised, 239/378 = 63+

% of judgments of active touch not affected, /378 = .2+

Under combination influences, the average is reduced to 4.14+ for

colors, and 3.12 for tones.

The next Table, V, shows the color-tone results for F. as Table IV

showed them for M. F.'s average for colors (Table I) alone was 4.35,

and was reduced in combination with tones by .26, or to 4.19. So, also,

F.'s average for tones alone (Table III), 4.33, was reduced by .74+

to 3.59. The averages in both cases show the same general tendency

to a lowering of the appreciation in both series when the series are

combined, but the tones are lowered more than the colors.

Table VI shows the effect of combining tones and active touches as

reported by M.

The effect of this combination is clear and unmistakeable. The

appreciation of the tones is raised 1.71+ points; and of the active

touches, .31+ points. This result is the opposite of that shown

in Table IV, where colors and tones were combined. There is this

agreement, however, that the appreciation of the tones is changed more

than that of the other stimuli. Relatively, the appreciation of the

touches changes least.

Table VII shows the effects on F. of combining tones and active

touches. The same general tendencies appear as in the case of M.; but

the changes in appreciation are not so marked. This is not easy to

explain, for F. estimated both the active touches and the tones higher

when taken alone than did M.

Table VIII shows the effect on F. of combining tones and passive

touches. The same general tendency to increased appreciation appears,

but the tones are raised more and the touches raised less than in

Table VII. This may be explained, perhaps, on the basis of increasing

appreciation with increased participation.

Tables IX and X show the effect on M. and F., respectively, of

combining colors and active touches. M. estimates both slightly higher,

while F. estimates both slightly lower. This difference cannot be

explained by the standards for each subject. From Tables I and III we

get:

_Standards._

_Colors._ _Active Touches._

M. 4.44 4.24

F. 4.35 4.55

With M. the colors go up to 4.87

With F. the colors go down to 4.22

With M. the active touches go up to 4.41

With F. the active touches go down to 4.17

Table VII. Tone-Active Touch Results. F.

_No. of times tone was_

_No. of_ _Not_ _No of points tone was_ _Net results_

_Tone_ _Raised_ _Lowered_ _affected_ _Raised_+ _Lowered_- + -

1 11 3 0 9.25 1.75 7.5

2 10 4 0 9.5 1 8.5

3 7 7 0 5.8 7.2 1.4

4 10 4 0 12 3.2 8.8

5 9 5 0 9.85 4.25 5.6

6 9 5 0 15.1 4.5 10.6

7 10 4 0 8 6.6 1.4

8 7 7 0 5.2 6.8 1.6

9 10 4 0 8 9 1

10 12 2 0 14.2 2.8 11.4

11 12 2 0 16 2.5 13.5

12 13 1 0 9.6 .8 8.8

13 13 1 0 12.2 .6 11.2

14 10 4 0 7 2.2 4.8

15 6 8 0 3 4 1

16 9 1 4 11 2 9

17 9 0 5 14 0 14

18 12 2 0 16.4 2.6 13.8

19 12 2 0 27.6 2.4 25.2

20 12 2 0 2.4 2.6 .2

21 14 0 0 4.2 0 4.2

22 14 0 0 17.2 0 17.2

23 4 5 5 6 5 1

24 0 14 0 0 9.6 9.6

25 7 5 2 5.6 6 .4

26 6 1 7 8 1 7

27 11 0 3 14 0 14

Totals, 259 93 26 197.5 15.2

Grand Total, 378 Net raised, 182.3

Averaging raising of each tone judgment, .48+

% of judgments of tones lowered, 93/378 = 24+

% of judgments of tones raised, 259/378 = 68+

% of judgments of tones not affected, 26/378 = 7-

_No of times touch was_

_No. of_ _Not_ _No. of points tone was_ _Net result_

_Touch_ _Raised_ _Lowered_ _affected_ _Raised_+ _Lowered_- + -

1 22 5 0 2.2 6.5 4.3

2 16 11 0 8.8 8.7 .1

3 20 7 0 7 5.6 1.4

4 19 8 0 5.8 11.4 5.6

5 18 9 0 14 7.5 6.5

6 16 11 0 6.8 9.7 2.9

7 13 5 9 13 5 8

8 13 14 0 13.1 12.2 .9

9 19 8 0 14.5 5 9.5

10 9 18 0 8.2 7.6 .6

11 22 5 0 8.6 3.5 5.1

12 15 12 0 15 4.8 10.2

13 22 1 4 35 1 34

14 20 7 0 26 1.4 24.6

Totals, 244 121 13 100.9 12.8

Grand Total, 378 Net raised, 88.1

Average raising of each active touch judgment, .23+

% of judgments of active touch lowered, 121/378 = 32+

% of judgments of active touch raised, 244/378 = 64+

% of judgments of active touch not affected, 13/378 = 3+

TABLE VIII. TONE-PASSIVE TOUCH RESULTS. F.

_No. of times tone was_

_No. of_ _Not_ _No. of points tone was_ _Net result_

Tone_ _Raised_ _Lowered_ _affected_ _Raised_ + _Lowered_ - + -

1 13 1 0 17.75 .25 17.5

2 12 2 0 18 0 18

3 13 1 0 11.2 .6 10.6

4 14 0 0 14.8 0 14.8

5 11 3 0 6.65 1.95 4.7

6 9 5 0 12.1 1.50 10.6

7 13 1 0 6.3 .9 5.4

8 14 0 0 17.4 0 17.4

9 6 8 0 5 4 1

10 14 0 0 20.4 0 20.4

11 14 0 0 12.5 0 12.5

12 10 4 0 7 5.2 1.8

13 14 0 0 10.6 0 10.6

14 12 2 0 8.4 .6 7.8

15 8 6 0 4 3 1

16 1 2 11 1 2 1

17 4 0 10 4 0 4

18 5 9 0 7 8.2 1.2

19 9 5 0 2.7 4.5 1.8

20 13 1 0 2.6 .8 1.8

21 13 1 0 3.9 .7 3.2

22 13 1 0 8.9 .7 8.2

23 6 2 6 10 2 8

24 12 2 0 15.2 .8 14.4

25 11 3 0 15.8 .6 15.2

26 0 6 8 0 8 8

27 10 0 4 13 0 13

Totals, 274 65 39 221.9 12.0

Grand Total, 378 Net raised, 209.9

Average raising of each tone judgment, .55+

% of judgments of tones lowered, 65/378 = 17+

% of judgments of tones raised, 274/378 = 72+

% of judgments of tones not affected, 39/378 = 10+

_No. of times touch was_

_No. of _Not_ _No. of points touch was_ _Net result_

Touch_ _Raised_ _Lowered_ _affected_ _Raised_ + _Lowered_ - + -

1 0 10 17 0 10 10

2 4 13 10 4 16 12

3 11 16 0 6.5 12 5.5

4 13 14 0 12.8 9.6 3.2

5 12 5 10 17 8 9

6 12 15 0 7.2 12 4.8

7 3 12 12 3 14 11

8 14 2 11 17 2 15

9 11 16 0 12.8 20.2 7.4

10 19 1 7 19 1 18

11 5 2 20 5 2 3

12 27 0 0 34.5 0 34.5

13 14 13 0 8.2 9.1 .9

14 17 10 0 25.6 2 23.6

Totals, 162 129 87 106.3 51.6

Grand Total, 378 Net raised, 54.7

Average raising of each passive touch judgment, .14+

% of judgments of passive touch lowered, 129/378 = 34

% of judgments of passive touch raised, 162/378 = 42

% of judgments of passive touch not affected, 87/378 = 23

TABLE IX. COLOR-ACTIVE TOUCH RESULTS. M.

_No. of times color was_

_No. of_ _Not_ _No. of points color was_ _Net result_

_Color_ _Raised_ _Lowered_ _affected_ _Raised_ + _Lowered_ - + -

1 5 1 8 5 1 4

2 0 7 7 0 7 7

3 3 11 0 1.8 4.4 2.6

4 3 11 0 2.4 4.2 1.8

5 3 11 0 2.4 2.2 .2

6 12 2 0 6 1 5

7 2 12 0 1.6 2.4 .8

8 12 0 2 12 0 12

9 13 1 0 14.2 .6 13.6

10 7 7 0 5.6 2.4 3.2

11 11 3 0 6.6 1.2 5.4

12 7 1 6 7 1 6

13 9 5 0 5.5 2.5 3

14 11 3 0 13.9 .3 13.6

15 11 0 3 12 0 12

16 10 4 0 8 1.2 6.8

17 12 2 0 16 1 15

18 14 0 0 24.8 0 24.8

19 0 0 14 0 0

20 9 5 0 7.2 1 6.2

21 1 0 13 1 0 1

22 14 0 0 5.2 0 5.2

23 14 0 0 10.2 0 10.2

24 8 0 6 14 0 14

25 9 5 0 6.3 1.5 4.8

26 4 1 9 4 1 3

27 11 3 0 4.3 .9 3.4

28 13 1 0 10.5 .5 10

Totals, 228 96 68 182.4 12.2

Grand Total, 392 Net raised, 170.2

Average raising of each color judgment, .43+

% of judgments of colors lowered, 96/392 = 24+

% of judgments of colors raised, 228/392 = 58+

% of judgments of colors not affected, 68/392 = 17+

_No. of times touch was_

_No. of _Not_ _No. of points touch was_ _Net Result_

Touch_ _Raised_ _Lowered_ _affected_ _Raised_ + _Lowered_ - + -

1 8 20 0 3.2 15 11.8

2 4 24 0 3.4 11.6 8.2

3 18 10 0 10 5 5

4 8 20 0 3.4 23 19.6

5 8 20 0 5 13 8

6 2 26 0 1.8 8.6 6.8

7 25 3 0 26.5 4.5 22

8 21 7 0 10.4 4.2 6.2

9 3 25 0 2.7 8.5 5.8

10 27 1 0 33.5 .5 33

11 23 5 0 3.3 4.5 1.2

12 22 0 6 41 0 41

13 26 2 0 42.6 .8 41.8

14 19 9 0 9.6 8.4 1.2

Totals 214 172 6 150.2 61.4

Grand Total, 392 raised, 88.8

Average raising of each active touch judgment, .22+

% of judgment of active touch, lowered, 172/392 = 43+

% of judgments of active touch raised, 214/392 = 54+

% of judgments of active touch not affected, 6/392 = 1.8+

TABLE X. COLOR-ACTIVE TOUCH RESULTS. F.

_No. of times color was_

_No. of_ _Not_ _No. of points color was_ _Net result_

_Color_ _Raised_ _Lowered_ _affected_ _Raised_ + _Lowered_ - + -

1 13 1 0 8.3 .9 2.4

2 5 4 5 5 6 1

3 2 5 7 2 5 3

4 9 5 0 7.6 3 4.6

5 9 5 0 16.2 7 9.2

6 0 14 0 0 20.4 20.4

7 3 11 0 2.1 5.3 3.2

8 1 3 10 1 3 2.0

9 5 9 0 3 8.2 5.2

10 9 5 0 10.95 8.25 2.7

11 12 2 0 8.6 1.4 7.2

12 8 6 0 9.8 2.4 7.4

13 4 1 9 6 1 5

14 10 4 0 11 1.6 9.4

15 2 12 0 2.8 3.2 .4

16 2 12 0 1.6 7.4 5.8

17 8 6 0 5 4 1

18 11 3 0 9.85 3.95 5.9

19 0 0 14 0 0

20 1 13 0 .8 14.4 13.6

21 2 7 5 2 7 5

22 8 6 0 11.4 9.2 2.2

23 0 14 0 0 11.4 11.4

24 0 10 4 0 10 10

25 2 12 0 3.8 10.2 6.4

26 0 14 0 0 11 11

27 0 14 0 0 8.6 8.6

28 2 12 0 1.8 6.2 4.4

Totals, 129 209 54 57 111.4

Grand total, 392 Net lowered, 54.4

Averaging lowering of each color judgment, .13+

% of judgments of colors lowered, 209/392 = 53+

% of judgments of colors raised, 129/392 = 32+

% of judgments of colors not affected, 54/392 = 13+

_No. of times touch was_

_No. of_ _Not_ _No. of points touch was_ _Net result_

_Touch_ _Raised_ _Lowered_ _affected_ _Raised_ + _Lowered_ - + -

1 11 17 0 1.1 28.3 27.2

2 14 14 0 11.2 13.8 2.6

3 19 9 0 9.8 7.2 2.6

4 11 17 0 2.2 25.6 23.4

5 13 15 0 12.5 16.5 4

6 12 16 0 4.6 12.2 7.6

7 15 0 13 23 0 23

8 2 26 0 .6 26.8 26.2

9 6 22 0 4 25 21

10 0 28 0 0 17.6 17.6

11 19 9 0 6.7 6.3 .4

12 3 25 0 3.8 10 6.2

13 2 26 0 2 32 30

14 8 20 0 6.4 19 12.6

Totals, 135 244 13 26.0 178.4

Grand Total, 392 Net lowered, 152.4

Average lowering of each active touch, .38+

% of judgments of active touch lowered, 244/392 = 62+

% of judgments of active touch raised, 135/392 = 34+

% of judgments of active touch not affected, 13/392 = 3+

TABLE XI. COLOR-PASSIVE TOUCH RESULTS. M.

_No. of times color was_

_No. of_ _Not_ _No. of points color was_ _Net Result_

_Color_ _Raised_ _Lowered_ _affected_ _Raised_ + _Lowered_ - + -

1 9 1 4 10 1 9

2 7 2 5 7 2 5

3 7 7 0 4.2 2.8 1.4

4 6 8 0 4.8 1.6 3.2

5 9 5 0 11.2 1 10.2

6 14 0 0 21 0 21

7 13 1 0 14.4 .2 14.2

8 11 0 3 14 0 14

9 14 0 0 18.6 0 18.6

10 7 7 0 5.6 1.4 4.2

11 10 4 0 7 2.6 4.4

12 3 3 8 3 3

13 13 1 0 12.5 .5 12

14 14 0 0 25.6 25.6

15 2 0 12 2 0 2

16 10 4 0 11 1.2 9.8

17 13 1 0 16.5 .5 16

18 13 1 0 13.9 .7 13.2

19 0 0 14 0 0

20 13 0 1 12.4 0 12.4

21 7 0 7 7 0 7

22 13 1 0 11.9 .7 11.2

23 14 0 0 18.2 0 18.2

24 12 0 2 22 0 22

25 14 0 0 15.8 0 15.8

26 9 0 5 9 0 9

27 12 2 0 9.4 .6 8.8

28 10 4 0 6 2 4

Totals, 279 52 61 292.2

Grand total, 392 Net raised, 292.2

Average raising of each color judgment, .75-

% of judgments of colors lowered, 52/392 = 13+

% of judgments of colors raised, 279/392 = 71+

% of judgments of colors not affected, 61/392 = 15+

_No. of times touch was_

_No. of_ _Not_ _No. of points touch was_ _Net Result_

_Touch_ _Raised_ _Lowered_ _affected_ _Raised_ + _Lowered_ - + -

1 0 3 25 0 3 3

2 5 13 10 5 16 11

3 5 10 13 5 12 7

4 8 3 17 9 3 6

5 6 2 20 6 3 3

6 5 11 12 5 12 7

7 1 19 8 1 27 26

8 12 0 16 12 0 12

9 22 0 6 23 0 23

10 21 0 7 22 0 22

11 28 0 0 24 0 24

12 16 0 12 19 0 19

13 22 6 0 32 3 29

14 20 0 8 22 0 22

Totals, 171 67 154 160 54

Grand total, 392 Net raised, 106

Average raising of each passive touch judgment, .27+

% of judgments of passive touch lowered, 67/392 = 17+

% of judgments of passive touch raised, 171/392 = 43+

% of judgments of passive touch not affected, 154/392 = 39+

TABLE XII. COLOR-PASSIVE TOUCH RESULTS. F.

_No. of times color was_

_No. of_ _Not_ _No. of points color was_ _Net Result_

_Color_ _Raised_ _Lowered_ _affected_ _Raised_ + _Lowered_ - + -

1 14 0 0 12.4 0 12.4

2 7 2 5 7 2 5

3 1 1 12 1 1

4 9 5 0 3.6 3 .6

5 14 0 0 15.2 0 15.2

6 0 14 0 0 2.4 2.4

7 13 1 0 9.1 .3 8.8

8 7 0 7 9 0 9

9 11 3 0 5.2 2.4 2.8

10 11 3 0 12.05 4.35 7.7

11 13 1 0 14.9 .7 14.2

12 4 10 0 2.4 6 3.6

13 1 1 12 1 1

14 11 3 0 6.6 1.2 5.4

15 9 5 0 4.5 .5 4

16 5 9 0 4 3.8 .2

17 12 2 0 6 2 4

18 13 1 0 12.55 .65 11.9

19 0 0 14 0 0

20 11 3 0 8.8 .6 8.2

21 10 0 4 11 0 11

22 10 4 0 14 1.2 12.8

23 3 11 0 4.7 1.1 3.6

24 2 0 12 2 0 2

25 4 10 0 5.8 1 4.8

26 7 7 0 4.5 3.5 1

27 11 3 0 7.6 1.2 6.4

28 12 2 0 10.8 .2 10.6

Totals, 226 100 66 161.6 6

Grand total, 392 Net raised, 155.6

Average raising of each color judgment, .40-

% of judgments of colors lowered, 100/392 = 25+

% of judgments of colors raised, 226/392 = 57+

% of judgments of colors not affected, 66/392 = 16+

_No. of times touch was_

_No. of_ _Not_ _No. of points touch was_ _Net Result_

_Touch_ _Raised_ _Lowered_ _affected_ _Raised_ + _Lowered_ - + -

1 0 8 20 0 8 8

2 3 14 11 3 15 12

3 23 5 0 14.5 2.5 12

4 17 11 0 11.2 4.4 6.8

5 21 1 6 27 1 26

6 16 12 0 9.6 5.8 3.8

7 4 10 14 4 10 6

8 13 7 8 14 7 7

9 17 11 0 18.6 3.2 15.4

10 15 1 12 15 1 14

11 0 1 27 0 1 1

12 28 0 0 21 0 21

13 21 7 0 18.3 7.9 10.4

14 24 4 0 31.2 1.8 29.4

Totals, 202 92 98 145.8 27

Grand total, 392 Net raised, 118.8

Average raising of each passive touch judgment, .30+

% of judgments of passive touch lowered, 92/392 = 23+

% of judgments of passive touch raised, 202/392 = 51+

% of judgments of passive touch not affected, 98/392 = 25+

Evidently no dynamic explanation of this difference is possible. It

has been impossible to reveal the cause of this particular difference;

in all other respects, however, the subjects agree in the general

tendencies revealed.

There remain the combinations of colors and passive touches. These

combinations are shown in Tables XI and XII.

In these tables the same general tendency to estimate both higher when

colors and passive touches are combined appears. M. raises the colors

more than F., and F. raises the touches more than M. This is perfectly

regular, as the following table shows:

_Standards._ _Raised in Combination to_

_Colors._ _Passive Touches._ _Colors._ _Passive Touches._

M. 4.44 5.14 5.16 5.40

F. 4.53 4.56 4.75 4.85

The whole results are recapitulated for both M. and F. in Table XIII.

TABLE XIII. RECAPITULATION

_Average_ _% of judgments of_ (----) _Av. + or - influ._

F. _Standard_ _Raised_ _Lowered_ _Not affected_ _on each_ (----)

1 Colors 4.35 28 59.6 11.9 (Color) - .26+

Tones 4.33 16 77 6 (Tone) - .74+

2 Colors 4.35 32 53 13 (Colors) - .13+

A. Touches 4.55 34 62 3 (A. T.) - .38+

3 Colors 4.35 57 25 16 (Colors) + .40+

P. Touches 4.56 51 23 25 (P. T.) + .30+

4 Tones 4.33 68 24 7 (Tones) + .45+

A. Touches 4.55 64 32 3 (A. T.) + .23+

5 Tones 4.33 72 17 10 (Tones) + .52+

P. Touches 4.56 42 34 23 (P. T.) + .14+

M.

1 Colors 4.44 23 59 17 (Color) - .29+

Tones 4.20 12 81 6 (Tones) - 1.08

2 Colors 4.44 58 24 17 (Colors) + .43+

A. Touches 4.24 54 43 1.8+ (A. T.) + .17+

3 Colors 4.44 71 13 15 (Colors) + .72+

P. Touches 5.14 43 17 39 (P.T.) + .26

4 Tones 4.20 99 .2 .5 (Tones) + 1.71+

A. Touches 4.24 63 36 .2 (A. T.) + .31+

From this last table certain conclusions may be drawn.

(1) When Colors and Tones were combined, both were lowered in the

appreciation of both subjects. The percentages show: (_a_) That about

the same number of colors was lowered, 59.6% for F. and 59% for M.

(_b_) That about the same average displacement of colors occurred, .26+

for F. and .29+ for M. (_c_) That about the same number of tones was

lowered, 77% for F. and 81% for M. (_d_) That the tones were lowered

more for M., -.74+ for F., and 1.08+ for M.

(2) When Colors and Active Touches were combined, for F. both are

lowered; for M. both are raised. The colors are lowered only very

slightly, .13 for F, while for M they are raised .43+; and conversely,

the active touches are lowered .38+ for F, and raised only .17+ for M.

Still, it appears clear that with F. there was an interference,--and

both colors and active touches are lowered while the same combinations

with M. are mutually reënforcing.

(3) When Colors and Passive Touches were combined, the appreciation of

both was raised for both F. and M. The result shows: (_a_) That the

percentages of colors and passive touches raised are practically the

same for both F. and M. (_b_) That the color displacement is greater

for M. than for F., being +.72+ for M. and only .40+ for F. (_c_) That

there is only a slight difference in the displacement of the passive

touches.

(4) When Tones and Active Touches were combined, the appreciation

of both was raised for both F. and M. It appears (_a_) that the

displacement for F. is very slight, .45+ and .23+, when compared

with the displacement for M., 1.71+ and .31+. But, (_b_) that the

displacement of tones is greater than that of the active touches for

both F. and M. (_c_) That this same relatively great displacement of

tones occurred in the opposite direction when colors and tones were

combined.

(5) When Tones and Passive Touches were combined, the appreciation of

both was raised for F,--the tones being raised more than the passive

touches. This combination was not tried with M. for lack of time.

From time to time some special tests of these general tendencies were

applied. From the results already set forth, one could predict that

there was a strong probability that when the tone-series was combined

with a constant touch-series, active or passive, the appreciation of

the tones would be raised. This was tried by allowing the subject M. to

rub his hand over the somewhat rough pillow of a tilting board. The

results showed that the appreciation of twenty-five out of twenty-seven

tones was raised. Other predictions were similarly verified.

Of course, any experiment of this nature is exposed to a great many

chances of error. The subjects may be fatigued, or depressed generally.

But the wide range of different readings taken is a reasonable

assurance that the chances of error are minimized. And it is to be

noted, also, that individual differences of appreciation do not vitiate

the results. In getting the "standards" no less than 2000 judgments

were given by each subject, while for the tables each subject gave

no less than 4000 judgments. The curves made from these data show

the effect of each separate combination by their variation from the

standard. The tables and analyses and conclusions already introduced

show, in general, that _our appreciation of each of several stimuli

in combination is different from our appreciation of the same stimuli

when taken separately_. The results show that this appreciation may be

either raised or lowered; that is to say, our feeling of values is not

constant for a given stimulus under all conditions.

From Table XIII I have found the average displacement of each series to

be as follows:

Tones, .90.

Colors, .37.

A. Touches, .28.

P. Touches, .23.

This shows that passive touches are subject to the least displacement,

while active touches, colors, and tones are respectively subject to

a greater variation. The sight-touch world is more stable than the

auditory world. With M. the tones go over a full point both below and

above the standard.

This report does not treat of the particular effects of a qualitative

nature that follow from the possible combinations of series of stimuli

of different feeling values,--such as the effect of an agreeable touch

upon a slightly disagreeable tone, or upon an indifferent color, and

so on. All such effects can be traced by rearranging the data already

collected, and this may be done in a subsequent paper which may enter

also into the theoretical discussion of the whole problem.

FOOTNOTE:

[Footnote 83: Attention may be called to the fact that this paper

arranges the conventional seven degrees of feelings in an order

opposite to that of the other papers of this volume; it follows still

the earlier traditions of our laboratory, while the more recent

investigations call very disagreeable 7 and very agreeable 1; the

indifference point remains the same.--EDITOR.]

THE COMBINATION OF FEELINGS

BY C. H. JOHNSTON

The problem at issue in the present investigation concerns the

combination of feelings. On the basis of theories as different in

many respects as those of Wundt, of Titchener, of Lipps, etc., the

feeling-state is always a unity. The affective process for Wundt

must be always "coextensive with consciousness." When he chooses to

speak of a "mixed feeling," it never for him signifies a "mosaic in

consciousness," but is always a new _Totalgefühl_, which "swamps

consciousness as a whole."

Titchener also believes that with every affective experience an

inevitable and pervasive "tilting" of the whole organism occurs. W.

McDougall, in his recent Physiological Psychology, makes the general

statement that always a "massive state of feeling results" when many

sensations are simultaneously excited, and that in such case we cannot

"introspectively distinguish the feeling-tone of each sensation."

We started to examine by experiment and by introspection which

feeling-effect really results from a combination of various impressions

with affective tone, and whether it is really impossible that various

feelings coexist and remain distinguishable. In case they can coexist,

the question arises: What mutual influences can be discovered?

For the main part of our study the simplest possible feelings were

chosen, because here presumably the subjects will not be forced to

grapple with complex personal psychoses, necessarily confusing from

their very richness. It was thought that here they could be more nearly

normal, naïve, less artificial, and able to a maximum to rid themselves

of preconceived personal opinions and unaccountable associations.

Here, with simplest stimulations, unsophisticated necessarily, the

hope at any rate is that work with a good number of subjects of

distinct emotional temperaments may bring to light certain fresh

simple introspective facts, which may in their turn offer valuable

considerations concerning the psychology of feeling.

Throughout the course of the experiment, except in the advanced stage

when more complex states were under consideration, sounds, colors,

odors, simple figures, and tactual surfaces were used. In the late

stage of the investigation sentences and pictures more or less morally

and æsthetically suggestive served to furnish for study the complex

feeling-states.

The progress of the investigation divides itself naturally into the

following four distinct parts.

I. From every experience of each individual the investigator sought to

obtain from the subject's own introspection at the time as adequate

a description as possible of the particular feeling provoked by the

chosen stimulus. The feelings studied in this first period of the

investigation are entirely those which heretofore have not been at

all classified except in terms of the objects which call them forth.

Part I is concerned with single stimuli affecting only one kind of

sense-organ, visual, tactual, auditory, or olfactory as the case may be.

Two requests were made of each subject, viz:

(_a_) To describe as clearly as possible how the particular experience

_felt_.

(_b_) To report always all the accompanying physiological or physical

processes which seemed to _mean_, to result from, or apparently

only accidentally to accompany the stimulus judged by him to have a

feeling-tone.

The work of the experiment covers a period of two years, and

fortunately several of the subjects were available for the whole

period. No subject was used for more than two hours each week. In the

preparatory training with sensations from only one sense-organ, the

range of colors, odors, etc., was chosen as follows: Twenty colors,

and as many tactual surfaces, etc., were presented in turn, and

each subject was requested to make his judgment as to the relative

degree of agreeableness or disagreeableness of the feelings arising

in the several cases. The scale of numbers from 1 to 7 served in

the traditional way to indicate approximately the hedonic value of

the feeling-tones, 1 signifying highest degree of pleasure, 2 very

pleasant, 3 slightly pleasant, 4 indifferent, 5 slightly unpleasant, 6

very unpleasant, and 7 the highest degree of unpleasantness. Though the

personal differences were in some cases rather striking, the individual

subject from day to day showed a relatively constant standard. This was

done in order simply to be able to choose approximately the stimulus

in the individual case likely to call up the _kind_ of feeling one

wished to study more in detail, and thus facilitate the progress of

the investigation. In this preliminary stage pleasant or unpleasant

seemed to the subjects more or less an exhaustive account of these

faint feelings. This was a means of eliminating practically indifferent

shades, as there is here no special interest in the psychology of color

as such.

* * * * *

II. Following upon this preparatory training, the second part of the

experiment consisted in a similar study of the _mutual influences_

of _simultaneous feelings_ accompanying sensations from different

sense-organs. How does the feeling of pleasure obtained from contact

with a smooth surface influence the feeling occasioned by the _sight_

of a pleasant or unpleasant object? Here, for example, colors were

exposed in a large black frame manipulated by means of shutters easily

opened or closed, at the same time that a tactual surface was being

applied, or a tone from a tuning-fork was being sounded.

The introspection method was essentially the same here as in Part I.

(_a_) First, the subject was requested, without the necessary

distraction of directing his attention at all to the bodily processes,

to give himself up to the situation and to report as accurately as he

could the kind of affective state experienced.

(_b_) Next, as in Part I again, in a repetition of the same experience,

he was requested to be on the lookout for any and all accompanying

bodily changes. The problem here was to discover to what extent the

more complex state now in question would correspond to the specific

and noticeable bodily reactions such as were noted in Part I, where

single experiences presumably resulted. If different feeling-elements

are in experience at once, can one fix upon correspondingly different

suggested actions? Does the organism react to more than one situation,

or to two sources of stimulation at once? Is affection present only

when the whole organism is, to use Titchener's expression, "tilted"

one way? Is the Totalgefühl the single undifferentiated result

always, or can we here also detect such phenomena as summation,

fusion, inhibition, and partial or total mutual reënforcement of the

different feeling-components? Do the new reactions which seem to mean

the feelings always refer to actions so inclusive as to result in the

inhibition of any other tendencies to response, or is there sometimes a

clear strife between two simultaneously conflicting feelings, two kinds

of relatively self-dependent reactions both going on at once? Or again,

when the hedonic or algedonic characters of two given simultaneous

stimuli, such as a soft, soothing, pleasant touch with an irritating,

exhilarating, invigorating but also pleasant yellow color, do not

differ as to their pleasant-unpleasant character, must one be pale and

empty "intellectual perception" when the other is being enjoyed? These

are some of the questions that suggest themselves at once.

Not at this point, however, considering the dimensionality of feeling,

the four simple combinations were first studied; such, for example, as

(1) a pleasant color with a pleasant touch, (2) pleasant color with

unpleasant touch, (3) unpleasant color with pleasant touch, and (4)

unpleasant color with unpleasant touch.

* * * * *

III. This part of the work was an attempt to estimate the average

time-interval in which feeling-tones develop, and what influences other

feelings given simultaneously or immediately beforehand have upon the

time-development of the feeling-tone in question. Will certain feelings

hasten and others retard a third feeling whose character remains

unchanged when it crosses the limen of awareness? Does the feeling, for

example, aroused by contact with a soft, soothing, yielding tactual

surface, put one in such a state that he will more or less quickly

obtain pleasure from the visual impression coming from a soft rich

red color? What effect will a feeling already aroused by a low tone

have upon the time development of the feeling one gets from looking

at a deep green color? Are there, again, pleasant feelings of certain

dimensions which will be hastened by other feelings, and still others

which, by the same means, will be retarded? If so, under what general

principle do they seem to fall?

Here the time-development of a certain feeling-tone is taken when

there are no other influencing factors. Then the comparison of this

rate is made with the later reported time-interval when that feeling,

again aroused, has been immediately preceded or accompanied by a

feeling-tone from another source of stimulation. Here also feelings

for colors presented in a frame, without any special suggestion of

form in connection with them, were in like manner compared as to

their time-development with the affective states arising from those

same colors presented again enclosed in cardboard frames of special

character. Some of these forms were very pleasing, such as upright

ovals, small circles, etc., while others, frames cut purposely into

irregular shapes, were to most observers decidedly unpleasant.

* * * * *

IV. Here complex feeling-states were in question, and evidence was

sought as to how much could be detected here that would tend to

substantiate or to call in question what seemed to be the fundamental

principles of feeling-relations where the states are very simple.

Further complications, such as three and even more stimulations at

once, were tested. After this, feelings aroused by looking at pictures

of statues were studied and described as accurately as possible. "Perry

Pictures" were used. _Dying Alexander_, _Venus of Milo_, the _Dying

Gladiator_, the _Laocoön_ group, and _Apollo Belvedere_, served to

introduce sufficient variety. Then copies of these same statues were

cut out from the card and presented to the subject with the same colors

before studied used as background. These were allowed to play their

part in the feeling aroused therefrom.

After this, pictures more or less morally as well as æsthetically

suggestive were used. Millet's _Angelus_ and his _Shepherdess Knitting_

and Rosa Bonheur's _Horse Fair_ afforded suggestion hints as to the

contrasted motor significance of the complex states called forth. Here

the attempt was made to find out in how far the feeling when once

aroused is dependent upon the retained after-images or memory-images

of the original visual stimulation, and what sort of feelings tend the

longer to persist. Or again when both are taken in in quick succession,

what sort of imagery and associations result. Are the resulting

associations or images colored by both feeling-tones in any definite

way? And if the feeling itself persists despite the loss of imagery,

can it be referred merely to more internal sensations, or does there

seem to be a necessity to consider it of purely central origin?

Such, in brief outline, has been the proposed method of study. In an

experiment of this delicate nature there are clearly many things to

guard against. There is danger that the investigator will unwittingly

make suggestions to the subjects by his questions. There is a great

danger of auto-suggestion on the part of the subject. The likelihood

is also considerable that the subjects will fall into stereotyped

forms of expression and general listlessness in introspection, where

from week to week these simple experiences are being repeated for

closer and closer examination. Again the special mood of the day will

necessarily tend to affect all such feeling-attitudes toward slight

stimulations supposed to have a feeling-tone. These and other dangers

were recognized at the outset, and avoided as much as possible by

such legitimate variations as could be introduced without changing

the general purpose of the work. No subject was used when he felt,

for whatever reason, unable to adapt himself to the conditions of the

experiment. No subject knew anything of the recorded results of the

others, and it was constantly urged that each person should wholly

regard the present feeling in question, ignoring any remembered tone

which that special stimulation had before afforded him.

It very soon became evident that the variations among individuals,

especially as to the amount of feeling and the consequent ability to

fix upon the special physical processes involved, were considerable.

The subjects represent types. Hence, it seems necessary at once to

mention briefly some characteristics of the persons themselves who have

reported these various experiences. This was kept in mind throughout,

and seems of decided significance in the interpretation of the recorded

results. After an examination of the results of each individual,

whatever remains that is common to all will be briefly summarized.

All the subjects were graduate students in Harvard University or in

Radcliffe College. Seven of the twelve had had from one to five or more

years' training in laboratory investigations. Two subjects were ladies,

the rest were gentlemen.

Subject A was a man of bright cheerful pleasant even temperament,

responsive, very musical, alert, physically vigorous, very careful in

statement, and decided as to the distinctness of his emotional states.

He uses his facial muscles a good deal while conversing.

Subject B is musical, sings a good deal, is not especially

demonstrative, nor always able to become adapted to the necessarily

oft-repeated stimulations from the same colors and tones. This subject

is especially discriminating as to shades, and has decided preferences

for certain colors.

Subject C usually found it difficult to find any decided feeling-tone

for many of the stimuli used. This subject is rather reserved and

undemonstrative as a rule. He is not at all musical, nor does he care

for art. He is a rather cool but extremely careful observer, and is

always guarded in his introspection.

Subject D is impulsive habitually, flashy, responsive, especially to

any suggestion of an æsthetic nature, such as forms, and very decided

as to his experiences. He walks with a quick nervous step, is sprightly

always, vivacious in conversation and outspoken.

Subject E is rather non-emotional as he often says. He is very

energetic, full of life, quick but not precise in all his movements,

always on a tension, does not enjoy without effort anything so mild as

the stimulations here used, and finds introspection of this affective

nature difficult.

Subject F is careful, experienced in introspective work, musical, talks

a great deal, enjoys this kind of work, has decided preferences, is

athletic and energetic. This subject makes use of facial, arm, and

shoulder gestures quite freely in general conversation.

Subject G has a penchant for talking a great deal, is decided in his

likes and dislikes, musical, of an uneven temperament, sometimes

cheerful, often cross, but always animated.

Subject H confesses he does not ever especially enjoy colors, nor

respond with any sign of demonstration to any situations. He is steady,

calm, apparently unruffled, and not an especially acute observer of his

own states, proving in this experiment unusually undiscriminative as to

simple experiences.

Subject I is rather morose, claiming to be habitually unmoved by even

display of great passion or excitement. He finds it generally much

easier to call up unpleasant than pleasant experiences, this being

exceptional among the subjects. He is much slower than the average, and

his feelings are not easily aroused. He is deliberative and confident

as to his state of mind. He is nervous and often becomes fatigued

before the hour's introspective work is over.

Subject J is nervous, of an uneven temperament, emotional, and quick

to react to a situation of any kind, and, rather more than the others,

subject to suggestion.

Subject K responds very quickly always, is habitually prompt and clear

in statement, of an even temperament, and unusually interested in the

experiment.

Subject L is unexperienced in this particular kind of work, but slow

and careful. Though athletic, his movements are rather heavy. He is

deliberate in speech and of an even, though rather undemonstrative

temperament. He also is musical.

In order to verify my somewhat personal descriptions here recorded a

questionnaire was given each subject to fill out according to his own

personal judgment of his emotional disposition. This was done toward

the close of the investigation, and the answers agree in the main with

the descriptions offered above.

For the first month's preliminary practice, and with the purpose of

stimulating curiosity and interest, and of testing the comparative

richness of even slight feeling-experiences, a great variety of

stimulations was used. Twenty different tactual surfaces from softest

plush to very rough sandpaper served for the tactual impressions.

Twelve different odors, as many colors differing in saturation and

intensity, and tones from high and low tuning-forks, and noises

variously produced, were employed as stimulations for the other senses.

Besides these, circles, upright and horizontal ovals of various sizes,

imperfect circles and ovals, and other irregular shapes were all

presented in the same large black frame. When studied alone indifferent

gray fillings were used. When complex states were in question colors

served as fillings. When the subjects thus became accustomed to these

very simple but very definitely _felt_ experiences, in these for the

most part habitually ignored affective elements of ordinary sensations,

the investigation at once became narrowed to more careful and minute

attention to a few of these feeling-tones. It was soon found also that

odors could not easily be used in combination, since they effectively

effaced all feeling-tones for the simultaneously given colors or

touches. Five colors, fairly representative for all subjects of

different kinds of feeling-tones, were chosen, and were used throughout

the whole investigation. These were the following: a soft deep red,

light brilliant yellow, deep pure green, saturated blue, and a dingy

greenish-yellow. The dimensions of the exposed surfaces were six by six

inches.

For tactual impressions of approximately equal value soft plush,

velvet, and two kinds of sandpaper were used, and for tones high and

low tuning-forks. All the above-named forms were used in connection

with the chosen colors. The subjects differed considerably as to the

_amount_ of feeling that could be obtained from such material. The

variation of kinds and of intensity in the same subject was sometimes

noticeable from day to day, but not great. It is hardly necessary to

give detailed quotations from each subject. The following summary of

the results of the experimental work, however, contains nothing that

was not frequently reported by a majority of the subjects. This, then,

does not represent at all what was once or occasionally reported by

individual subjects, but what after training seemed to be reliable and

definite and constant feeling-states.

PART I

_Section A._ The following are the collected expressions which many

subjects used to describe the feeling for this _particular shade of

red_. It feels as if it would be soft. It suggests warmth. The feeling

is one of seriousness, pleasantness, quietness, of free repose,--a

full feeling of the sense of safety. It is soothing, rich, full of

strength, and inviting. One feels restful, grave, calm, appeased. There

is an agreeable longing and a tendency to lose one's self in the color.

The feeling is one of comfort, luxury, satisfaction, expansiveness,

tranquillity, and quiescence, with no accompanying feeling of weakness

by exertion of effort or energy. There is neither marked tension on the

one hand, nor collapse on the other. There is a sense rather of easy

self-control and command of one's body, but with no aggressive sorrow

nor joy element,--a feeling of being attracted, with nothing to suggest

any obstacle to the adaptation.

Occasionally to all subjects this color, and, indeed, all colors,

seemed "dead," arousing no feeling whatever. Here the color "ought

to be pleasant," but is only "for the time potentially not actually

actively pleasant." Still more rarely did this red appear to be

unpleasant. Some subjects thought that this afforded the greatest

_amount of sensual pleasure_. More than any of the other colors they

think it appears to "give you something." It does not so much stimulate

as furnish a content itself. It has a direct effect rather than a

tendency to make one wish to do something and thus give pleasure

from the activity itself. Only one subject failed to find this color

pleasant. His early association of it with blood and ghastly scenes

could not be overcome. Some others, when a glare or glaze appeared on

the red, found in it slight suggestions of stimulation and excitement,

but the general decision in the great majority of cases was that the

feeling was a sort of emotional massiveness compared with the effects

from other colors.

In marked contrast, for the most part, appears the characteristic

feeling-tone for our chosen shade of _yellow_. Almost universally

subjects find such words as these descriptive of the feeling here

in question. It is cheerful, brisk, pleasant[84] also, bright, gay,

light, sprightly, merry, jovial, easy to get, pleasantly irritating,

stimulating, stirring, spurring, thrilling, invigorating, and produces

agreeable discontent. It is jolly, nice, trim, neat, awakening, full of

the sense of motion, soaring, and arouses a feeling of welcome strain,

of pleasure in action, of alertness and self-assertion. Here, in

contrast for the most part to the red, there is no feeling of sinking

into the color. The impulse rather is to be free, to enjoy motor

expression, even if of some vague sort. There is a _felt_ necessity to

do something, a "joy of overflowing or of exuberance," it is called.

There is little present here of what we mean by a suggestion of sensual

richness found above in the feeling for red. Here there is less of

amount of pleasure, but much more of the general activity element. Some

subjects feel the demand for greater saturation, and occasionally it is

unpleasant for just this reason apparently. Subjects C and B frequently

reported this. They think the feeling would be more "stable" and

"grave" and "secure" and "soothing" and one would not feel "unruffled,"

if it could be "toned down." Most of the subjects, however, think that

it belongs to the ultimate elemental feeling for yellow that it should

have just this distinguishing characteristic.

It is more difficult to describe the feeling for _green_. It is almost

always agreeable. Two subjects, however, never like it. Sometimes it

is somewhat soothing in character, but more often it is exciting.

The feeling seems to be between that for red and that for yellow,

partaking on the whole of the characters of feeling for the latter

rather than the former. For all subjects associations tend to color

the feeling-tone for green especially, and hence introspection for

the feeling of pure color is doubly difficult. The most prominent

partial feeling-tone for it is "irritating."[85] The agreeableness

or disagreeableness of this stimulating character is particularly

inconstant, varying greatly for the same subject, as well as for

different subjects.

The feeling for the _blue_ seems still more to be dependent upon

the person. Many like it. Many others dislike it decidedly. When it

affords a pleasant feeling, it is described in some such terms as

these: The feeling is spiritual, lofty, beautiful, serene. The subject

himself feels immoveable. To other subjects it is too rich and intense

and painful. To one subject who heartily dislikes it always, it is

offensive or revolting, calling up a feeling akin to the emotion one

has toward insincerity in general. To none does this feeling seem

to have any great amount of sensual significance. Even when it is

called "too rich," the incongruity between the richness itself and the

ultimate qualitative significance of the blue is spoken of. Even when

pleasant, the feeling is of an "airy pleasure," volatile, unstable, and

not reliable, nor safe and secure as is the feeling for red. One feels

that it is always apt to vanish, vague, intangible, and with little

immediate definiteness of meaning. Subjects often desire to call it an

intellectual, æsthetic, or ideal sort of feeling.

No color was universally unpleasant. Two subjects found this

_greenish-yellow_ almost always mildly pleasant. For most of the

subjects, however, it was unpleasant. Here were reported feelings of

contraction, of withdrawal, of disgust, of doubt, of hesitation, of

stimulation without definiteness, dissatisfaction, slight feeling

of nausea, of sea-sickness, of opposition, and the general feeling

of offensiveness. The necessary, unpleasant aggressiveness, unrest,

or discontent characterizes this feeling. This unpleasant critical

attitude where a decision is wanted but not easily gotten, is called

often the feeling of uncertainty.

In no sense is this investigation a study of the psychology of color;

the only purpose here is to find certain clearly defined feelings

for slight stimulations, in order to find in what way they relate

themselves to other similarly simple feelings from a different source

of stimulation.

In a similar manner, then, the investigation was conducted in the

analysis and description of feeling-tones for _tactual impressions_.

For _plush_ there was a feeling of pleasure, ease, safety, and content.

The mood was one of a general enjoyment of sinking one's self into

the situation, an agreeable self-surrender. Here also is a feeling

of unbending one's self, of general expansiveness, of relaxation.

One is soothed, enjoys a suggestion of freedom from disturbance, of

a "regularity" of the experience, feels at the same time strength in

the suggested repose, responds to pleasant reverberating thrills by

the falling off from the accustomed muscular tonicity, and hence has a

decided feeling of satisfaction. To some subjects the feeling aroused

by the hard, polished, glazed tin surface, possessing no "yielding"

character, corresponded more nearly to the feeling for the yellow

color than for the red. To all red "went best" with the plush. No

tactual feelings offered such distinguishable elements for analysis,

nor were they as definitely described as the visual or olfactory or

auditory impressions. The sensational elements were in many cases more

pronounced. The feeling for the plush, however, much like that for

the red color, suggests a "settling down to," or a "dropping forward

toward," rather than an aggressive "taking in" of the feeling-material.

The feeling-tone with sensations from sandpaper is grating, irritating,

stirring, stimulating. The feeling is one of contraction, of

withdrawal, of uneasiness. One is full of "collapsing chills," of

minute little pains, and there is a decided call for an opposite kind

of behavior. The sense of weakness, of waste of power and energy, of

being penetrated, of strained expectation, of unwelcome tension, and of

slight "wasteful excitement" results. To some subjects, notably subject

E, at times the whole feeling of stimulation as such predominated,

and the total effect produced was agreeable, as it "satisfied a felt

need of waking up." Here again one subject, subject B, throughout the

whole period of two years, failed to find any element of pleasure in

any tactual sensation that was pronounced or prolonged sufficiently to

furnish material for introspection.

As regards simple _tones_ from tuning-forks the subjects find little

to say. All are pleasant, as a rule, and almost universally, _low

tones_ are most pleasant, richer in content, greater in amount of

"general appeal," more soothing, and pleasantly stimulating. The

feeling of the easy attitude called for contributes to the whole

feeling. _High tones_, calling for more activity on the part of the

subject, more strain, and greater stimulation, coupled with some rather

unprepared-for irritating elements, are less pleasant, and also more

limited in their general appeal to the whole organism. The noises

variously produced were at first unpleasant, and the only assignable

reason seemed to be that their suddenness came as a shock. If expected

or continued they too became pleasant very often.

Feelings for _forms_ seem to relate even more definitely to the

activity element. The pleasure for the most part is described as

being far less sensual, if indeed, so at all. Small _upright ovals_,

1-1/2 × 1 in., are most pleasant, because somehow they are "more

suggestive of definiteness." _Circles_ one inch in diameter are next

in order of value as to their feeling-tones. _Horizontal ovals_ are

less pleasant still, though for most subjects not unpleasant. Upright

ovals are best, as the kind of action apparently called for by the

aroused feeling is most agreeable and suitable to the subject's

natural upright position of body. An explanation of this general

result of introspection, as well as the preference for the particular

size chosen almost without exception, is attempted in another part

of this report, where are given in more detail the various kinds of

bodily accompaniments. The feelings for those ovals have also the

characters of stimulation, mild excitement, and a feeling of easy

freedom in a pleasing kind of activity. Tension is always present as

an agreeable element when reported at all. This element is coupled

with the "feeling of assurance of certainty" which the whole situation

calls for. It often seems clearly to suggest that one do something.

Circles tend more to suggest inner stability and completeness. They

stand on their own axes. Here there is a sense of satisfaction,

complacency, and sufficiency. The feeling here of a call for immediate

activity on the part of the subject is weak and indefinite, when not

altogether absent. The subjects do not use for this experience such

expressions as excitement, tension, irritation, quick contraction, or

the impulse to self-assertion. Horizontal ovals are least pleasant, it

seems to me, for obvious reasons. Here such noted elements as "felt

unnaturalness," "difficulty of adapting one's self," "wrong direction

of activity," which alone and in themselves would be unpleasant, are

nevertheless more than counterbalanced by other and pleasing elements,

such as symmetry, definiteness, partial stability, and other agreeable

features. Often these latter features are not pronounced, and then the

judgment is, that the total feeling is unpleasant.

Likewise as regards so-called bad forms, no single statement is

unqualifiedly true of any considerable number of subjects. The

decided feeling of irregularity, the "bulging-out" or the undesirable

"pushing-in" of the figure, the feeling of weakness in one's own body

corresponding, the feeling of instability which one tends himself to

imitate in various ways, the total effect of lack of poise, all tend

to make these figures on the whole unpleasant. But one cannot even

here count upon the constancy of the subjects' feelings. At times, due

perhaps to undercurrents of association processes of which even the

subject himself is not clearly aware, the figure suddenly looms up as

quite definitely pleasing, and full of vague suggestiveness and hidden

richness of content. These varying characters of the feelings for

forms come out interestingly later in the study of them when they are

presented as frames for the above described colors.

* * * * *

_Section B._ The bodily processes noted by the subjects are numerous,

and here also, just as with the amount of feeling above, the personal

differences are striking. Some subjects detect a great many forms of

organic commotion, others rarely find anything that can be said to be

descriptive or explanatory of the feeling-state. To all of them at

first this looking for bodily accompaniments destroyed the feeling

itself. Only after considerable training was it possible for them to

find any physiological processes that seemed at all significant. As a

general statement the evidence would all tend to suggest that feelings

for color are most readily and directly referred to the head, face,

throat, and particularly to the forehead and to the eye-muscles. When,

however, the feelings are particularly strong, they tend to pervade the

whole organism. Red thus often brings about the suggestion of general

bodily comfort, and yellow, when very strong, arouses the impulses

calling for "spreading-out, aggressive movements," referred to arms,

shoulders, and chest. Tones have in general the same reference to

the head. Odors are always more organic, affecting more directly the

respiration, muscles of the abdomen, and the more internal apparatus

generally. Tactual impressions refer to the trunk rather than to

the face, hand, arms, or legs. Forms seem to call forth imitative

movements, and the actual or incipient motor impulses refer to the

action of the eyes in motion, the position of the head, of the whole

body, of the shoulders particularly, of the shaping of the cheeks,

lips, etc., and of the similarly imitative actions in the hands and

arms. The following is a list collected from the reported bodily

references given for the feelings described in Part I, Section A.

(1) Free full respiration and free activity of all voluntary muscles;

or, for other feelings, the checking of respiration and often the lack

of impulse to move at all, with no suggestion, however, in most cases,

of lassitude.

(2) Chest expansion and general relief pervading the whole body.

The expansion or contraction is further modified by the _degree_ of

_regularity_ and by the _rate_ of the movements involved, as also by

the ease or _difficulty_ in the performance. So also, in the cases of

feeling whose tone exists but is doubtful in character, the bodily

situation seems to mean "lack of movement or change in any definite

direction." The feeling-tone and its vividness are interdependent and

reported as closely connected.

(3) A cringing all over and a "holding up of all activities."

(4) Abdomen contraction, chest and shoulders drawn in, hands clenched,

and jaws set.

(5) A feeling at once in different parts of the body of both process of

contraction and expansion.

(6) An incipient feeling of nausea in the digestive tract.

(7) A tendency to incline the head forward or backward, or to keep it

rigid, or to turn it aside.

(8) For touch, waves, reverberations, pleasant penetrating thrills

in the chest and abdomen especially, less frequently in the limbs,

occur. Sometimes these suggest expansion of the whole frame; sometimes,

even when also pleasant, the tendency to contraction and tension is

noticeable, but in these latter cases the contraction seems to be

rather definitely the calling into action of those general innervated

muscles which refer to the bodily situation of one when he intends to

go toward the pleasantly stimulating object.

(9) For unpleasant touch the reference or localization of the bodily

response is, when reported definitely at all, generally in the back,

described as chills not thrills, contractions always, contractions also

which often suggest shivers of withdrawal. These feelings also are

referred to the situation of the trunk of the body, and are felt to

originate in the small of the back, and in the back of the shoulders.

For two subjects there occur twitchings in the tendons of the hips and

thighs, and movements of the knee-cap.

(10) The pervasive bodily collapse, which seems to accompany feelings

characterized as depressing, altogether unlike the soothing feeling of

unwearied repose given by certain soft rich colors or by low deep full

tones or smooth yielding surfaces, is another form of organic response

which is often spoken of.

(11) The direction of the stimulus with respect to the normal position

of the body also seems to have something to do with the regularity

of the response, and with the general forward or backward tendency.

Tactual surfaces applied or tones sounded behind the subject do seem

to make the bodily adjustment more confused, and less pleasant. All

that subjects could say was that the position was felt as abnormal and

correspondingly less pleasing.

(12) In many unpleasant feelings, where there was no specific

localization possible, the "stiffening tendency of hardening one's self

to a necessary experience" was frequently reported. In the case of

other states of undifferentiated pleasure a "consenting bending forward

of the whole body" was often detected.

(13) Many stimulations seem to demand that one draw one's self erect,

square the shoulders, and "assume the attitude of alertness."

(14) Certain colors for almost every subject independently hint at

sea-sickness. Others, as noted above, report the incipient suggestion

of nausea in the digestive tract. Indeed, abdominal references are

frequently reported by most of the subjects. The abdominal muscles

become "eased up," or again there is a "sucking-in of the belly."

(15) The feeling of "being natural," of regularity, a universally

popular feeling, is described as a pleasant relief from all tensions

and habitual inhibitions, or a dropping of one's characteristic

muscular tonicity.

(16) Other stimulations still, particularly certain delicate odors, for

men, subjects C and E for example, seem to suggest what they call the

"childish play impulse." They are called "simple, foolish, childish

pleasures," ignored in ordinary life. They are slightly pleasantly

irritating, and merely make one wish to do something. It is pure

bodily restlessness, a general kinæsthetic enjoyment. Three subjects,

especially, find here the frequent twitchings in the calves of the

legs, in the knee-cap, and the more decided innervations which contract

the tendons of the thighs and hips.

(17) Subject I frequently detected sensations of contraction in the

tensor tympani connected with the pleasure derived from high tones.

Others referred feelings for tones partly to the regions of the ears.

(18) The kinds of facial references are numerous. General contraction

or expansion around the eyes, forehead, temples, sometimes to the whole

head, and quite frequently it seemed as if the feeling referred to the

very inside of the eyeball, to the iris and accommodation movements.

(19) Subjects A, D, F, and K noted specific incipient tendencies to

smile, to smooth the brow, and to "unbend the face" as characteristic

descriptions of certain oft-repeated experiences.

(20) Introspections from subjects F and G quite constantly revealed

articulatory impulses vividly accompanying the feelings for many colors

and forms.

(21) A scowl and puckering of the lips was descriptive of the attitude

taken toward some unpleasant situations.

(22) A contraction or relaxation of the throat-muscles and of the vocal

chords generally was not infrequently noticed. The tendency to swallow

is spoken of. The throat is felt often to be "concave" when certain

bad feelings are sufficiently pronounced. A contraction in the mucous

membrane, with teeth on edge, such as one would experience in eating

something sour, is frequent. A twitching of the ears, squinting of the

eyebrows, and a "heavy feeling" through the neck and chest occur often,

or again a pressing hard of the tongue against the roof of the mouth.

(23) Forms suggested a shrinking in the volume of the face, sometimes

of the crown of the head, and even of the whole head.

(24) Upright or horizontal ovals especially provoked the impulse to

imitate the figure itself, either with the lips or with the hands and

arms. When the feeling was particularly strong, all these impulses

often occurred together and appeared mutually to reënforce, or to

intensify each other.

(25) Horizontal ovals gave one the feeling of being "flattened out,"

coupled with an impulse to adjustment altogether unlike the sprightly,

alert, airy feeling aroused by the "trim," upright figures.

(26) Occasionally when the irregular shapes were presented directly

after a subject had been enjoying one of the perfect figures, that

side of his face or body corresponding to the distorted portion of

the figure was felt to be in an abnormal and unpleasant position.

This "caving-in" or "bulging-out" sensation, which accompanies the

unpleasant feeling, happens when the whole muscular system at the time

for the subject seems inert or externally controlled.

All these sensations of bodily processes, taken from the introspective

descriptions given by the subjects, are distinctly reported by them

as very faint. They by no means detect them in every experience, nor

do they always seem to the subject himself to _mean_ the whole of

the feeling as experienced. Neither did any one subject find all the

concomitant processes recorded above. Subject H failed throughout the

whole period to detect anything whatsoever, except slight tendencies

to frown, smooth the brow, or to open wide the eyes. This subject was

unable to detect any special differences in his feelings, either in

variety or in amount. For him neither soft red nor brilliant yellow

was either exciting or soothing. They were and always remained for him

more or less vaguely pleasant, and this description for him was both

ultimate and exhaustive.

Subject B could get no kind of pleasant feeling from any tactual

surface, while to Subject E even the coarsest sandpaper usually

afforded pleasant stimulation. As spoken of above, articulatory

impulses were characteristic of the motor tendencies of Subjects D

and G. To Subject A the experiences seemed richest and fullest, and

the corresponding bodily processes were likewise more pronounced and

varied. In the great majority of the experiments, especially during

the period of training, the feeling itself vanished when the subjects

attempted to analyze the bodily processes. It was chiefly, however, a

matter of training, and this more and more ceased to be a disturbing

element.

Some subjects preferred often to speak of circulatory, or at least,

decidedly internal and usually involuntary changes in addition to, and

sometimes without, the controlled muscular actions. The mood of the

time affects the amount of feeling, and occasionally, but far less

frequently, the quality. The moral significance of the feelings was

most prominent when the subject felt most interested in the experiment,

as may be noted above in their descriptions of the feelings for red

and yellow. What may be termed the "_regularity element_" would seem

generally to serve as the test especially for the pleasant-unpleasant

character of the feeling-tone. The feeling of expansiveness never

accompanied unpleasant feelings. Feelings of contraction, on the

other hand, very often occurred when the feelings were not at all

disagreeable. In such cases there was a significance attached to the

direction or meaning of the adjustment.