HALF HOURS
WITH
MODERN SCIENTISTS.
LECTURES AND ESSAYS
BY
PROFS. HUXLEY, BARKER, STIRLING, COPE AND TYNDALL.
WITH
A GENERAL INTRODUCTION
BY
NOAH PORTER, D.D., LL.D.,
PRESIDENT OF YALE COLLEGE.
FIRST SERIES.
[Illustration]
NEW HAVEN, CONN.:
CHARLES C. CHATFIELD & CO.,
1872.
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Entered according to act of Congress, in the year 1872, by
CHARLES C. CHATFIELD & CO.,
In the Office of the Librarian of Congress, at Washington, D. C.
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NEW HAVEN, CONN.:
THE COLLEGE COURANT PRINT.
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Electrotyped by E. B. Sheldon, New Haven, Conn.
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CONTENTS.
GENERAL INTRODUCTION. BY PREST. PORTER, v
ON THE PHYSICAL BASIS OF LIFE. 1
PROF. T. H. HUXLEY,
CORRELATION OF VITAL AND PHYSICAL 37
FORCES.
PROF. G. F. BARKER, M.D.,
AS REGARDS PROTOPLASM—REPLY TO HUXLEY. 73
JAMES HUTCHISON STIRLING,
ON THE HYPOTHESIS OF EVOLUTION. 145
PROF. E. D. COPE,
SCIENTIFIC ADDRESSES.
ON THE METHODS AND TENDENCIES OF 219
PHYSICAL INVESTIGATION,
ON HAZE AND DUST, 234
ON THE SCIENTIFIC USE OF THE 247
IMAGINATION,
PROF. JOHN TYNDALL, LL.D., F.R.S., 217
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INTRODUCTION TO THE NEW EDITION OF HALF HOURS WITH MODERN SCIENTISTS.
The title of this Series of Essays—_Half Hours with Modern
Scientists_—suggests a variety of thoughts, some of which may not be
inappropriate for a brief introduction to a new edition. _Scientist_ is
a modern appellation which has been specially selected to designate a
devotee to one or more branches of physical science. Strictly
interpreted it might properly be applied to the student of any
department of knowledge when prosecuted in a scientific method, but for
convenience it is limited to the student of some branch of physics. It
is not thereby conceded that nature, _i.e._, physical or material nature
is any more legitimately or exclusively the field for scientific
enquiries than spirit, or that whether the objects of science are
material or spiritual, the assumptions and processes of science
themselves should not be subjected to scientific analysis and
justification. There are so-called philosophers who adopt both these
conclusions. There are those who reason and dogmatize as though nature
were synonymous with matter, or as though spirit, if there be such an
essence, must be conceived and explained after the principles and
analogies of matter;—others assume that a science of scientific method
can be nothing better than the mist or moonshine which they vilify by
the name of metaphysics. But unfortunately for such opinions the fact is
constantly forced upon the attention of scientists of every description,
that the agent by which they examine matter is more than matter, and
that this agent, whatever be its substance, asserts its prerogatives to
determine the conceptions which the scientist forms of matter as well as
to the methods by which he investigates material properties. Even the
positivist philosopher who not only denounces metaphysics as
illegitimate, but also contends that the metaphysical era of human
inquiry, has in the development of scientific progress been outgrown
like the measles, which is experienced but once in a life-time; finds
when his positivist theory is brought to the test that positivism itself
in its very problem and its solutions, is but the last adopted
metaphysical theory of science.
We also notice that it is very difficult, if not impossible, for the
inquisitive scientist to limit himself strictly to the object-matter of
his own chosen field, and not to enquire more or less earnestly—not
infrequently to dogmatize more or less positively—respecting the results
of other sciences and even respecting the foundations and processes of
scientific inquiry itself. Thus Mr. Huxley in the first Essay of this
Series on _The Physical Basis of Life_, leaves the discussion of his
appropriate theme in order to deliver sundry very positive and
pronounced assertions respecting the “limits of philosophical inquiry,”
and quotes with manifest satisfaction a dictum of David Hume that is
sufficiently dogmatic and positive, as to what these limits are. In more
than one of his Lay sermons, he rushes headlong into the most pronounced
assertions in respect to the nature of matter and of spirit. The
eloquent Tyndall, in No. 5, expounds at length _The Methods and
Tendencies of Physical Investigation_ and discourses eloquently, if
occasionally somewhat poetically, of _The Scientific use of the
Imagination_. But Messrs. Huxley and Tyndall are eminent examples of
scientists who are severely and successfully devoted respectively to
physiology and the higher physics. No one will contend that they have
not faithfully cultivated their appropriate fields of inquiry. The fact
that neither can be content to confine himself within his special field,
forcibly illustrates the tendency of every modern science to concern
itself with its relations to its neighbors, and the unresistible
necessity which forces the most rigid physicist to become a
metaphysician in spite of himself. So much for the appellation
“_Scientists_.”
“_Half Hours_” suggests the very natural inquiry—What can a scientist
communicate in half an hour, especially to a reader who may be ignorant
of the elements of the science which he would expound? Does not the
phrase _Half Hours with Modern Scientists_ stultify itself and suggest
the folly of any attempt to treat of science with effect in a series of
essays? In reply we would ask the attention of the reader to the
following considerations.
The tendency is universal among the scientific men of all nations, to
present the principles of science in such brief summaries or statements
as may bring them within the reach of common readers. The tendency
indicates that there is a large body of readers who are so far
instructed in the elements of science as to be able to understand these
summaries. In England, Germany, France and this country such brief
essays are abundant, either in the form of contributions to popular and
scientific journals, or in that of popular lectures, or in that of brief
manuals, or of monographs on separate topics; especially such topics as
are novel, or are interesting to the public for their theoretic
brilliancy, or their applications to industry and art.
These essays need not be and they are not always superficial, because
they are brief. They often are the more profound on account of their
conciseness, as when they contain a condensed summary of the main
principles of the art or science in question, or a brief history of the
successive experiments which have issued in some brilliant discovery.
These essays are very generally read, even though they are both concise
and profound. But they could not be read even though they were less
profound than they are, were there not provided a numerous company of
readers who are sufficiently instructed in science to appreciate them.
That such a body of readers exists in the countries referred to, is
easily explained by the existence of public schools and schools of
science and technology, by the enormous extension of the knowledge of
machinery, engineering, mining, dyeing, etc., etc., all of which imply a
more or less distinct recognition of scientific principles and stimulate
the curiosity in regard to scientific truth. Popular lectures also,
illustrated by experiments, have been repeated before thousands of
excited listeners, and the eager and inventive minds of multitudes of
ingenious youths have been trained by this distribution of science, to
the capacity to comprehend the compact and pointed scientific essay,
even though it taxes the attention and suspends the breath for a
half-hour by its closeness and severity.
The fact is also worthy of notice, that many of the ablest scientists of
our times have made a special study of the art of expounding and
presenting scientific truth. Some of them have schooled themselves to
that lucid and orderly method by which a science seems to spring into
being a second time, under the creative hand of its skilful expositor.
Others have made a special study of philosophic diction. Others have
learned how to adorn scientific truth with the embellishments of an
affluent imagination. Some of the ablest writers of our time are found
among the devotees of physical science. That a few scientific writers
and lecturers may have exemplified some of the most offensive features
of the demagogue and the sophist cannot be denied, but we may not forget
that many have attained to the consummate skill of the accomplished
essayist and impressive and eloquent orator.
One advantage cannot be denied of this now popular and established
method of setting forth scientific truth, viz., that it prescribes a
convenient method of bringing into contrast the arguments _for_ and
_against_ any disputed position in science. If materialism can furnish
its ready advocate with a convenient vehicle for its ready diffusion,
the antagonist theory can avail itself of a similar vehicle for the
communication of the decisive and pungent reply. The one is certain to
call forth the other, and if the two are present side by side in the
same series, so much the better is it for the truth and so much the
worse for the error. The teacher before his class, the lecturer in the
presence of his audience, has the argument usually to himself; he allows
few questionings and admits no reply. An erroneous theory may entrench
itself within a folio against arguments which would annihilate its
positions if these were condensed in a tract.
This consideration should dispel all the alarm that is felt by the
defenders of religion in view of the general diffusion of popular
scientific treatises. The brief statement of a false or groundless
scientific theory, even by its defender, is often its most effectual
refutation. A magnificently imposing argument often shrinks into
insignificance when its advocate is forced to state its substance in a
compact and close-jointed outline. The articulations are seen to be
defective, the joints do not fit one another, the coherence is
conspicuously wanting. Let then error do its utmost in the field of
science. Its deficient data and its illogical processes are certain to
be exposed, sometimes even by its own advocates. If this does not happen
the defender of that scientific truth which seems to be essential to the
teachings and faiths of religion, must scrutinize its reasonings by the
rules and methods of scientific inquiry. If science seems to be hostile
to religion, this very seeming should arouse the defender of Theism and
Christianity to examine into the grounds both by the light and methods
which are appropriate to science itself. The more brief and compact and
popular is the argument which he is to refute, the more feasible is the
task of exposure and reply. Only let this be a cardinal maxim with the
defender of the truth, that whatever is scientifically defended and
maintained must be scientifically refuted and overthrown. The great
Master of our faith never uttered a more comprehensive or a grander
maxim than the memorable words, “_To this end was I born and for this
cause came I into the world, that I should bear witness unto the truth.
Everyone that is of the truth heareth my voice._” It would be easy to
show that the belief in moral and religious truth and the freedom in
searching for and defending it which was inspired by these words have
been most efficient in training the human mind to that faith in the
results of scientific investigation which characterize the modern
scientist. That Christian believer must either have a very imperfect
view of the spirit of his own faith, or a very narrow conception of the
evidences and the effect of its teachings, who imagines that the freest
spirit of scientific inquiry, or the most penetrating insight into the
secrets of matter or of spirit can have any other consequence than to
strengthen and brighten the evidence for Christian truth.
N. P.
YALE COLLEGE, _May_, 1872.
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PUBLISHERS’ NOTE TO SECOND EDITION.
The five lectures embodied in this First Series of Half Hours with
Modern Scientists were first published as Nos. I.—V. of the University
Scientific Series. In this series the publishers have aimed to give to
the public in a cheap pamphlet form, the advance thought in the
Scientific world. The intrinsic value of these lectures has created a
very general desire to have them put in a permanent form. They therefore
have brought them out in this style. Each five succeeding numbers of
this celebrated series will be printed and bound in uniform style with
this volume, and be designated as second series, third series, and so
on. Henceforth it will be the design of the publishers to give
preference to those lectures and essays of American scientists which
contain original research and discovery, rather than to reprinting from
European sources. The lectures in the second series will be (1) On
Natural Selection as Applied to Man, by Alfred Russel Wallace; (2) three
profoundly interesting lectures on Spectrum Analysis, by Profs. Roscoe,
Huggins, and Lockyer; (3) the Sun and its Different Atmospheres, a
lecture by Prof. C. A. Young, Ph.D., of Dartmouth College; (4) the Earth
a great Magnet, by Prof. A. M. Mayer, Ph.D., of Stevens Institute; and
(5) the Mysteries of the Voice and Ear, by Prof. Ogden N. Rood, of
Columbia College. The last three lectures contain many original
discoveries and brilliant experiments, and are finely illustrated.
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_ON THE PHYSICAL BASIS OF LIFE._
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INTRODUCTION.
The following remarkable discourse was originally delivered in
Edinburgh, November 18th, 1868, as the first of a series of Sunday
evening addresses, upon non-religious topics, instituted by the Rev. J.
Cranbrook. It was subsequently published in London as the leading
article in the _Fortnightly Review_, for February, 1869, and attracted
so much attention that five editions of that number of the magazine have
already been issued. It is now re-printed in this country, in permanent
form, for the first time, and will doubtless prove of great interest to
American readers. The author is Thomas Henry Huxley, of London,
Professor of Natural History in the Royal School of Mines, and of
Comparative Anatomy and Physiology in the Royal College of Surgeons. He
is also President of the Geological Society of London. Although
comparatively a young man, his numerous and valuable contributions to
Natural Science entitle him to be considered one of the first of living
Naturalists, especially in the departments of Zoölogy and Paleontology,
to which he has mainly devoted himself. He is undoubtedly the ablest
English advocate of Darwin’s theory of the Origin of Species,
particularly with reference to its application to the human race, which
he believes to be nearly related to the higher apes. It is, indeed,
through his discussion of this question that he is, perhaps, best known
to the general public, as his late work entitled “Man’s Place in
Nature,” and other writings on similar topics, have been very widely
read in this country and in Europe. In the present lecture Professor
Huxley discusses a kindred subject of no less interest and importance,
and should have an equally candid hearing.
YALE COLLEGE, _March_ 30_th_, 1869.
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On the Physical Basis of Life.
In order to make the title of this discourse generally intelligible, I
have translated the term “Protoplasm,” which is the scientific name of
the substance of which I am about to speak, by the words “the physical
basis of life.” I suppose that, to many, the idea that there is such a
thing as a physical basis, or matter, of life may be novel—so widely
spread is the conception of life as a something which works through
matter, but is independent of it; and even those who are aware that
matter and life are inseparably connected, may not be prepared for the
conclusion plainly suggested by the phrase “the physical basis or matter
of life,” that there is some one kind of matter which is common to all
living beings, and that their endless diversities are bound together by
a physical, as well as an ideal, unity. In fact, when first apprehended,
such a doctrine as this appears almost shocking to common sense. What,
truly, can seem to be more obviously different from one another in
faculty, in form, and in substance, than the various kinds of living
beings? What community of faculty can there be between the
brightly-colored lichen, which so nearly resembles a mere mineral
incrustation of the bare rock on which it grows, and the painter, to
whom it is instinct with beauty, or the botanist, whom it feeds with
knowledge?
Again, think of the microscopic fungus—a mere infinitesimal ovoid
particle, which finds space and duration enough to multiply into
countless millions in the body of a living fly; and then of the wealth
of foliage, the luxuriance of flower and fruit, which lies between this
bald sketch of a plant and the giant pine of California, towering to the
dimensions of a cathedral spire, or the Indian fig, which covers acres
with its profound shadow, and endures while nations and empires come and
go around its vast circumference! Or, turning to the other half of the
world of life, picture to yourselves the great finner whale, hugest of
beasts that live, or have lived, disporting his eighty or ninety feet of
bone, muscle and blubber, with easy roll, among waves in which the
stoutest ship that ever left dockyard would founder hopelessly; and
contrast him with the invisible animalcules—mere gelatinous specks,
multitudes of which could, in fact, dance upon the point of a needle
with the same ease as the angels of the schoolmen could, in imagination.
With these images before your minds, you may well ask what community of
form, or structure, is there between the animalcule and the whale, or
between the fungus and fig-tree? And, _a fortiori_, between all four?
Finally, if we regard substance, or material composition, what hidden
bond can connect the flower which a girl wears in her hair and the blood
which courses through her youthful veins; or, what is there in common
between the dense and resisting mass of the oak, or the strong fabric of
the tortoise, and those broad disks of glassy jelly which may be seen
pulsating through the waters of a calm sea, but which drain away to mere
films in the hand which raises them out of their element? Such
objections as these must, I think, arise in the mind of every one who
ponders, for the first time, upon the conception of a single physical
basis of life underlying all the diversities of vital existence; but I
propose to demonstrate to you that, notwithstanding these apparent
difficulties, a threefold unity—namely, a unity of power or faculty, a
unity of form, and a unity of substantial composition—does pervade the
whole living world. No very abstruse argumentation is needed, in the
first place, to prove that the powers, or faculties, of all kinds of
living matter, diverse as they may be in degree, are substantially
similar in kind. Goethe has condensed a survey of all the powers of
mankind into the well-known epigram:
“Warum treibt sich das Volk so und schreit? Es will sich
ernähren Kinder zeugen, und sie nähren so gut es vermag.
* * * * *
Weiter bringt es kein Mensch, stell’ er sich, wie er auch will.”
In physiological language this means, that all the multifarious and
complicated activities of man are comprehensible under three categories.
Either they are immediately directed towards the maintenance and
development of the body, or they effect transitory changes in the
relative positions of parts of the body, or they tend towards the
continuance of the species. Even those manifestations of intellect, of
feeling, and of will, which we rightly name the higher faculties, are
not excluded from this classification, inasmuch as to every one but the
subject of them, they are known only as transitory changes in the
relative positions of parts of the body. Speech, gesture, and every
other form of human action are, in the long run, resolvable into
muscular contraction, and muscular contraction is but a transitory
change in the relative positions of the parts of a muscle. But the
scheme, which is large enough to embrace the activities of the highest
form of life, covers all those of the lower creatures. The lowest plant,
or animalcule, feeds, grows and reproduces its kind. In addition, all
animals manifest those transitory changes of form which we class under
irritability and contractility; and it is more than probable, that when
the vegetable world is thoroughly explored, we shall find all plants in
possession of the same powers, at one time or other of their existence.
I am not now alluding to such phenomena, at once rare and conspicuous,
as those exhibited by the leaflets of the sensitive plant, or the
stamens of the barberry, but to much more widely-spread, and, at the
same time, more subtle and hidden, manifestations of vegetable
contractility. You are doubtless aware that the common nettle owes its
stinging property to the innumerable stiff and needle-like, though
exquisitely delicate, hairs which cover its surface. Each
stinging-needle tapers from a broad base to a slender summit, which,
though rounded at the end, is of such microscopic fineness that it
readily penetrates, and breaks off in, the skin. The whole hair consists
of a very delicate outer case of wood, closely applied to the inner
surface of which is a layer of semi-fluid matter, full of innumerable
granules of extreme minuteness. This semi-fluid lining is protoplasm,
which thus constitutes a kind of bag, full of a limpid liquid, and
roughly corresponding in form with the interior of the hair which it
fills. When viewed with a sufficiently high magnifying power, the
protoplasmic layer of the nettle hair is seen to be in a condition of
unceasing activity. Local contractions of the whole thickness of its
substance pass slowly and gradually from point to point, and give rise
to the appearance of progressive waves, just as the bending of
successive stalks of corn by a breeze produces the apparent billows of a
corn-field. But, in addition to these movements, and independently of
them, the granules are driven, in relatively rapid streams, through
channels in the protoplasm which seem to have a considerable amount of
persistence. Most commonly, the currents in adjacent parts of the
protoplasm take similar directions; and, thus, there is a general stream
up one side of the hair and down the other. But this does not prevent
the existence of partial currents which take different routes; and,
sometimes, trains of granules may be seen coursing swiftly in opposite
directions, within a twenty-thousandth of an inch of one another; while,
occasionally, opposite streams come into direct collision, and, after a
longer or shorter struggle, one predominates. The cause of these
currents seem to lie in contractions of the protoplasm which bounds the
channels in which they flow, but which are so minute that the best
microscopes show only their effects, and not themselves.
The spectacle afforded by the wonderful energies prisoned within the
compass of the microscopic hair of a plant, which we commonly regard as
a merely passive organism, is not easily forgotten by one who has
watched its display continued hour after hour, without pause or sign of
weakening. The possible complexity of many other organic forms,
seemingly as simple as the protoplasm of the nettle, dawns upon one; and
the comparison of such a protoplasm to a body with an internal
circulation, which has been put forward by an eminent physiologist,
loses much of its startling character. Currents similar to those of the
hairs of the nettle have been observed in a great multitude of very
different plants, and weighty authorities have suggested that they
probably occur, in more or less perfection, in all young vegetable
cells. If such be the case, the wonderful noonday silence of a tropical
forest is, after all, due only to the dullness of our hearing; and could
our ears catch the murmur of these tiny maelstroms, as they whirl in the
innumerable myriads of living cells which constitute each tree, we
should be stunned, as with the roar of a great city.
Among the lower plants, it is the rule rather than the exception, that
contractility should be still more openly manifested at some periods of
their existence. The protoplasm of _Algæ_ and _Fungi_ becomes, under
many circumstances, partially, or completely, freed from its woody case,
and exhibits movements of its whole mass, or is propelled by the
contractility of one or more hair-like prolongations of its body, which
are called vibratile cilia. And, so far as the conditions of the
manifestation of the phenomena of contractility have yet been studied,
they are the same for the plant as for the animal. Heat and electric
shocks influence both, and in the same way, though it may be in
different degrees. It is by no means my intention to suggest that there
is no difference in faculty between the lowest plant and the highest, or
between plants and animals. But the difference between the powers of the
lowest plant, or animal, and those of the highest is one of degree, not
of kind, and depends, as Milne-Edwards long ago so well pointed out,
upon the extent to which the principle of the division of labor is
carried out in the living economy. In the lowest organism all parts are
competent to perform all functions, and one and the same portion of
protoplasm may successively take on the function of feeding, moving, or
reproducing apparatus. In the highest, on the contrary, a great number
of parts combine to perform each function, each part doing its allotted
share of the work with great accuracy and efficiency, but being useless
for any other purpose. On the other hand, notwithstanding all the
fundamental resemblances which exist between the powers of the
protoplasm in plants and in animals, they present a striking difference
(to which I shall advert more at length presently,) in the fact that
plants can manufacture fresh protoplasm out of mineral compounds,
whereas animals are obliged to procure it ready-made, and hence, in the
long run, depend upon plants. Upon what condition this difference in the
powers of the two great divisions of the world of life depends, nothing
is at present known.
With such qualification as arises out of the last-mentioned fact, it may
be truly said that the acts of all living things are fundamentally one.
Is any such unity predicable of their forms? Let us seek in easily
verified facts for a reply to this question. If a drop of blood be drawn
by pricking one’s finger, and viewed with proper precautions and under a
sufficiently high microscopic power, there will be seen, among the
innumerable multitude of little, circular, discoidal bodies, or
corpuscles, which float in it and give it its color, a comparatively
small number of colorless corpuscles, of somewhat larger size and very
irregular shape. If the drop of blood be kept at the temperature of the
body, these colorless corpuscles will be seen to exhibit a marvelous
activity, changing their forms with great rapidity, drawing in and
thrusting out prolongations of their substance, and creeping about as if
they were independent organisms. The substance which is thus active is a
mass of protoplasm, and its activity differs in detail, rather than in
principle, from that of the protoplasm of the nettle. Under sundry
circumstances the corpuscle dies and becomes distended into a round
mass, in the midst of which is seen a smaller spherical body, which
existed, but was more or less hidden, in the living corpuscle, and is
called its _nucleus_. Corpuscles of essentially similar structure are to
be found in the skin, in the lining of the mouth, and scattered through
the whole frame work of the body. Nay, more; in the earliest condition
of the human organism, in that state in which it has just become
distinguishable from the egg in which it arises, it is nothing but an
aggregation of such corpuscles, and every organ of the body was, once,
no more than such an aggregation. Thus a nucleated mass of protoplasm
turns out to be what may be termed the structural unit of the human
body. As a matter of fact, the body, in its earliest state, is a mere
multiple of such units; and, in its perfect condition, it is a multiple
of such units, variously modified. But does the formula which expresses
the essential structural character of the highest animal cover all the
rest, as the statement of its powers and faculties covered that of all
others? Very nearly. Beast and fowl, reptile and fish, mollusk, worm,
and polype, are all composed of structural units of the same character,
namely, masses of protoplasm with a nucleus. There are sundry very low
animals, each of which, structurally, is a mere colorless
blood-corpuscle, leading an independent life. But, at the very bottom of
the animal scale, even this simplicity becomes simplified, and all the
phenomena of life are manifested by a particle of protoplasm without a
nucleus. Nor are such organisms insignificant by reason of their want of
complexity. It is a fair question whether the protoplasm of those
simplest forms of life, which people an immense extent of the bottom of
the sea, would not outweigh that of all the higher living beings which
inhabit the land, put together. And in ancient times, no less than at
the present day, such living beings as these have been the greatest of
rock builders.
What has been said of the animal world is no less true of plants.
Imbedded in the protoplasm at the broad, or attached, end of the nettle
hair, there lies a spheroidal nucleus. Careful examination further
proves that the whole substance of the nettle is made up of a repetition
of such masses of nucleated protoplasm, each contained in a wooden case,
which is modified in form, sometimes into a woody fibre, sometimes into
a duct or spiral vessel, sometimes into a pollen grain, or an ovule.
Traced back to its earliest state, the nettle arises as the man does, in
a particle of nucleated protoplasm. And in the lowest plants, as in the
lowest animals, a single mass of such protoplasm may constitute the
whole plant, or the protoplasm may exist without a nucleus. Under these
circumstances it may well be asked, how is one mass of non-nucleated
protoplasm to be distinguished from another? why call one “plant” and
the other “animal?” The only reply is that, so far as form is concerned,
plants and animals are not separable, and that, in many cases, it is a
mere matter of convention whether we call a given organism an animal or
a plant.
There is a living body called _Æthalium septicum_, which appears upon
decaying vegetable substances, and in one of its forms, is common upon
the surface of tan pits. In this condition it is, to all intents and
purposes, a fungus, and formerly was always regarded as such; but the
remarkable investigations of De Bary have shown that, in another
condition, the _Æthalium_ is an actively locomotive creature, and takes
in solid matters, upon which, apparently, it feeds, thus exhibiting the
most characteristic feature of animality. Is this a plant, or is it an
animal? Is it both, or is it neither? Some decide in favor of the last
supposition, and establish an intermediate kingdom, a sort of biological
No Man’s Land for all these questionable forms. But, as it is admittedly
impossible to draw any distinct boundary line between this no man’s land
and the vegetable world on the one hand, or the animal, on the other, it
appears to me that this proceeding merely doubles the difficulty which,
before, was single. Protoplasm, simple or nucleated, is the formal basis
of all life. It is the clay of the potter; which, bake it and paint it
as he will, remains clay, separated by artifice, and not by nature, from
the commonest brick or sun-dried clod. Thus it becomes clear that all
living powers are cognate, and that all living forms are fundamentally
of one character.
The researches of the chemist have revealed a no less striking
uniformity of material composition in living matter. In perfect
strictness, it is true that chemical investigation can tell us little or
nothing, directly, of the composition of living matter, inasmuch as such
matter must needs die in the act of analysis, and upon this very obvious
ground, objections, which I confess seem to me to be somewhat frivolous,
have been raised to the drawing of any conclusions whatever respecting
the composition of actually living matter from that of the dead matter
of life, which alone is accessible to us. But objectors of this class do
not seem to reflect that it is also, in strictness, true that we know
nothing about the composition of any body whatever, as it is. The
statement that a crystal of calc-spar consists of carbonate of lime, is
quite true, if we only mean that, by appropriate processes, it may be
resolved into carbonic acid and quicklime. If you pass the same carbonic
acid over the very quicklime thus obtained, you will obtain carbonate of
lime again; but it will not be calc-spar, nor anything like it. Can it,
therefore, be said that chemical analysis teaches nothing about the
chemical composition of calc-spar? Such a statement would be absurd; but
it is hardly more so than the talk one occasionally hears about the
uselessness of applying the results of chemical analysis to the living
bodies which have yielded them. One fact, at any rate, is out of reach
of such refinements, and this is, that all the forms of protoplasm which
have yet been examined contain the four elements, carbon, hydrogen,
oxygen, and nitrogen, in very complex union, and that they behave
similarly towards several reagents. To this complex combination, the
nature of which has never been determined with exactness, the name of
Protein has been applied. And if we use this term with such caution as
may properly arise out of our comparative ignorance of the things for
which it stands, it may be truly said, that all protoplasm is
proteinaceous; or, as the white, or albumen, of an egg is one of the
commonest examples of a nearly pure protein matter, we may say that all
living matter is more or less albuminoid. Perhaps it would not yet be
safe to say that all forms of protoplasm are affected by the direct
action of electric shocks; and yet the number of cases in which the
contraction of protoplasm is shown to be affected by this agency
increases, every day. Nor can it be affirmed with perfect confidence
that all forms of protoplasm are liable to undergo that peculiar
coagulation at the temperature of 40 degrees—50 degrees centigrade,
which has been called “heat-stiffening,” though Kühne’s beautiful
researches have proved this occurrence to take place in so many and such
diverse living beings, that it is hardly rash to expect that the law
holds good for all. Enough has, perhaps, been said to prove the
existence of a general uniformity in the character of the protoplasm, or
physical basis of life, in whatever group of living beings it may be
studied. But it will be understood that this general uniformity by no
means excludes any amount of special modifications of the fundamental
substance. The mineral, carbonate of lime, assumes an immense diversity
of characters, though no one doubts that under all these Protean changes
it is one and the same thing.
And now, what is the ultimate fate, and what the origin of the matter of
life? Is it, as some of the older naturalists supposed, diffused
throughout the universe in molecules, which are indestructible and
unchangeable in themselves; but, in endless transmigration, unite in
innumerable permutations, into the diversified forms of life we know?
Or, is the matter of life composed of ordinary matter, differing from it
only in the manner in which its atoms are aggregated? Is it built up of
ordinary matter, and again resolved into ordinary matter when its work
is done? Modern science does not hesitate a moment between these
alternatives. Physiology writes over the portals of life,
“Debemur morti nos nostraque,”
with a profounder meaning than the Roman poet attached to that
melancholy line. Under whatever disguise it takes refuge, whether fungus
or oak, worm or man, the living protoplasm not only ultimately dies and
is resolved into its mineral and lifeless constituents, but is always
dying, and, strange as the paradox may sound, could not live unless it
died. In the wonderful story of the “Peau de Chagrin,” the hero becomes
possessed of a magical wild ass’s skin, which yields him the means of
gratifying all his wishes. But its surface represents the duration of
the proprietor’s life; and for every satisfied desire the skin shrinks
in proportion to the intensity of fruition, until at length life and the
last handbreadth of the “Peau de Chagrin,” disappear with the
gratification of a last wish. Balzac’s studies had led him over a wide
range of thought and speculation, and his shadowing forth of
physiological truth in this strange story may have been intentional. At
any rate, the matter of life is a veritable “Peau de Chagrin,” and for
every vital act it is somewhat the smaller. All work implies waste, and
the work of life results, directly or indirectly, in the waste of
protoplasm. Every word uttered by a speaker costs him some physical
loss; and, in the strictest sense, he burns that others may have
light—so much eloquence, so much of his body resolved into carbonic
acid, water and urea. It is clear that this process of expenditure
cannot go on forever. But, happily, the protoplasmic _peau de chagrin_
differs from Balzac’s in its capacity of being repaired, and brought
back to its full size, after every exertion. For example, this present
lecture, whatever its intellectual worth to you, has a certain physical
value to me, which is, conceivably, expressible by the number of grains
of protoplasm and other bodily substance wasted in maintaining my vital
processes during its delivery. My _peau de chagrin_ will be distinctly
smaller at the end of the discourse than it was at the beginning.
By-and-by, I shall probably have recourse to the substance commonly
called mutton, for the purpose of stretching it back to its original
size. Now this mutton was once the living protoplasm, more or less
modified, of another animal—a sheep. As I shall eat it, it is the same
matter altered, not only by death, but by exposure to sundry artificial
operations in the process of cooking. But these changes, whatever be
their extent, have not rendered it incompetent to resume its old
functions as matter of life. A singular inward laboratory, which I
possess, will dissolve a certain portion of the modified protoplasm, the
solution so formed will pass into my veins; and the subtle influences to
which it will then be subjected will convert the dead protoplasm into
living protoplasm, and transubstantiate sheep into man. Nor is this all.
If digestion were a thing to be trifled with, I might sup upon lobster,
and the matter of life of the crustacean would undergo the same
wonderful metamorphosis into humanity. And were I to return to my own
place by sea, and undergo shipwreck, the crustacea might, and probably
would, return the compliment, and demonstrate our common nature by
turning my protoplasm into living lobster. Or, if nothing better were to
be had, I might supply my wants with mere bread, and I should find the
protoplasm of the wheat-plant to be convertible into man, with no more
trouble than that of the sheep, and with far less, I fancy, than that of
the lobster. Hence it appears to be a matter of no great moment what
animal, or what plant, I lay under contribution for protoplasm, and the
fact speaks volumes for the general identity of that substance in all
living beings. I share this catholicity of assimilation with other
animals, all of which, so far as we know, could thrive equally well on
the protoplasm of any of their fellows, or of any plant; but here the
assimilative powers of the animal world cease.
A solution of smelling-salts in water with an infinitesimal proportion
of some other saline matters, contains all the elementary bodies which
enter into the composition of protoplasm; but, as I need hardly say, a
hogshead of that fluid would not keep a hungry man from starving, nor
would it save any animal whatever from a like fate. An animal cannot
make protoplasm, but must take it ready-made from some other animal, or
some plant—the animal’s highest feat of constructive chemistry being to
convert dead protoplasm into that living matter of life which is
appropriate to itself. Therefore, in seeking for the origin of
protoplasm, we must eventually turn to the vegetable world. The fluid
containing carbonic acid, water, and ammonia, which offers such a
barmecide feast to the animal, is a table richly spread to multitudes of
plants; and with a due supply of only such materials, many a plant will
not only maintain itself in vigor, but grow and multiply until it has
increased a million-fold, or a million million-fold, the quantity of
protoplasm which it originally possessed; in this way building up the
matter of life, to an indefinite extent, from the common matter of the
universe. Thus the animal can only raise the complex substance of dead
protoplasm to the higher power, as one may say, of living protoplasm;
while the plant can raise the less complex substances—carbonic acid,
water, and ammonia—to the same stage of living protoplasm, if not to the
same level. But the plant also has its limitations. Some of the fungi,
for example, appear to need higher compounds to start with, and no known
plant can live upon the uncompounded elements of protoplasm. A plant
supplied with pure carbon, hydrogen, oxygen, and nitrogen, phosphorus,
sulphur, and the like, would as infallibly die as the animal in his bath
of smelling-salts, though it would be surrounded by all the constituents
of protoplasm. Nor, indeed, need the process of simplification of
vegetable food be carried so far as this, in order to arrive at the
limit of the plant’s thaumaturgy.
Let water, carbonic acid, and all the other needful constituents, be
supplied without ammonia, and an ordinary plant will still be unable to
manufacture protoplasm. Thus the matter of life, so far as we know it
(and we have no right to speculate on any other) breaks up in
consequence of that continual death which is the condition of its
manifesting vitality, into carbonic acid, water, and ammonia, which
certainly possess no properties but those of ordinary matter; and out of
these same forms of ordinary matter and from none which are simpler, the
vegetable world builds up all the protoplasm which keeps the animal
world agoing. Plants are the accumulators of the power which animals
distribute and disperse.