To appreciate his work, something must be known of the life of the man.

He was born near Maria-Einsiedeln, in Switzerland, the son of a poor

physician of the place. He began the study of medicine under the

instruction of his father, and later on came under the instruction

of several learned churchmen. At the age of sixteen he entered the

University of Basel, but, soon becoming disgusted with the philosophical

teachings of the time, he quitted the scholarly world of dogmas and

theories and went to live among the miners in the Tyrol, in order that

he might study nature and men at first hand. Ordinary methods of study

were thrown aside, and he devoted his time to personal observation--the

only true means of gaining useful knowledge, as he preached and

practised ever after. Here he became familiar with the art of mining,

learned the physical properties of minerals, ores, and metals, and

acquired some knowledge of mineral waters. More important still, he

came in contact with such diseases, wounds, and injuries as miners are

subject to, and he tried his hand at the practical treatment of these

conditions, untrammelled by the traditions of a profession in which his

training had been so scant.

Having acquired some empirical skill in treating diseases, Paracelsus

set out wandering from place to place all over Europe, gathering

practical information as he went, and learning more and more of the

medicinal virtues of plants and minerals. His wanderings covered a

period of about ten years, at the end of which time he returned to

Basel, where he was soon invited to give a course of lectures in the

university.

These lectures were revolutionary in two respects--they were given in

German instead of time-honored Latin, and they were based upon personal

experience rather than upon the works of such writers as Galen and

Avicenna. Indeed, the iconoclastic teacher spoke with open disparagement

of these revered masters, and openly upbraided his fellow-practitioners

for following their tenets. Naturally such teaching raised a storm of

opposition among the older physicians, but for a time the unparalleled

success of Paracelsus in curing diseases more than offset his

unpopularity. Gradually, however, his bitter tongue and his coarse

personality rendered him so unpopular, even among his patients, that,

finally, his liberty and life being jeopardized, he was obliged to flee

from Basel, and became a wanderer. He lived for brief periods in Colmar,

Nuremberg, Appenzell, Zurich, Pfeffers, Augsburg, and several other

cities, until finally at Salzburg his eventful life came to a close in

1541. His enemies said that he had died in a tavern from the effects

of a protracted debauch; his supporters maintained that he had been

murdered at the instigation of rival physicians and apothecaries.

But the effects of his teachings had taken firm root, and continued

to spread after his death. He had shown the fallibility of many of the

teachings of the hitherto standard methods of treating diseases, and

had demonstrated the advantages of independent reasoning based on

observation. In his Magicum he gives his reasons for breaking with

tradition. "I did," he says, "embrace at the beginning these doctrines,

as my adversaries (followers of Galen) have done, but since I saw that

from their procedures nothing resulted but death, murder, stranglings,

anchylosed limbs, paralysis, and so forth, that they held most diseases

incurable.... therefore have I quitted this wretched art, and sought for

truth in any other direction. I asked myself if there were no such thing

as a teacher in medicine, where could I learn this art best? Nowhere

better than the open book of nature, written with God's own finger." We

shall see, however, that this "book of nature" taught Paracelsus some

very strange lessons. Modesty was not one of these. "Now at this time,"

he declares, "I, Theophrastus Paracelsus, Bombast, Monarch of the

Arcana, was endowed by God with special gifts for this end, that every

searcher after this supreme philosopher's work may be forced to imitate

and to follow me, be he Italian, Pole, Gaul, German, or whatsoever or

whosoever he be. Come hither after me, all ye philosophers, astronomers,

and spagirists.... I will show and open to you... this corporeal

regeneration."(1)

Paracelsus based his medical teachings on four "pillars"--philosophy,

astronomy, alchemy, and virtue of the physician--a strange-enough

equipment surely, and yet, properly interpreted, not quite so anomalous

as it seems at first blush. Philosophy was the "gate of medicine,"

whereby the physician entered rightly upon the true course of learning;

astronomy, the study of the stars, was all-important because "they (the

stars) caused disease by their exhalations, as, for instance, the sun by

excessive heat"; alchemy, as he interpreted it, meant the improvement of

natural substances for man's benefit; while virtue in the physician was

necessary since "only the virtuous are permitted to penetrate into the

innermost nature of man and the universe."

All his writings aim to promote progress in medicine, and to hold before

the physician a grand ideal of his profession. In this his views are

wide and far-reaching, based on the relationship which man bears

to nature as a whole; but in his sweeping condemnations he not only

rejected Galenic therapeutics and Galenic anatomy, but condemned

dissections of any kind. He laid the cause of all diseases at the door

of the three mystic elements--salt, sulphur, and mercury. In health he

supposed these to be mingled in the body so as to be indistinguishable;

a slight separation of them produced disease; and death he supposed to

be the result of their complete separation. The spiritual agencies of

diseases, he said, had nothing to do with either angels or devils, but

were the spirits of human beings.

He believed that all food contained poisons, and that the function of

digestion was to separate the poisonous from the nutritious. In the

stomach was an archaeus, or alchemist, whose duty was to make this

separation. In digestive disorders the archaeus failed to do this, and

the poisons thus gaining access to the system were "coagulated" and

deposited in the joints and various other parts of the body. Thus the

deposits in the kidneys and tartar on the teeth were formed; and the

stony deposits of gout were particularly familiar examples of this. All

this is visionary enough, yet it shows at least a groping after rational

explanations of vital phenomena.

Like most others of his time, Paracelsus believed firmly in the doctrine

of "signatures"--a belief that every organ and part of the body had a

corresponding form in nature, whose function was to heal diseases of

the organ it resembled. The vagaries of this peculiar doctrine are too

numerous and complicated for lengthy discussion, and varied greatly from

generation to generation. In general, however, the theory may be summed

up in the words of Paracelsus: "As a woman is known by her shape, so are

the medicines." Hence the physicians were constantly searching for some

object of corresponding shape to an organ of the body. The most natural

application of this doctrine would be the use of the organs of the lower

animals for the treatment of the corresponding diseased organs in

man. Thus diseases of the heart were to be treated with the hearts of

animals, liver disorders with livers, and so on. But this apparently

simple form of treatment had endless modifications and restrictions,

for not all animals were useful. For example, it was useless to give the

stomach of an ox in gastric diseases when the indication in such cases

was really for the stomach of a rat. Nor were the organs of animals the

only "signatures" in nature. Plants also played a very important role,

and the herb-doctors devoted endless labor to searching for such plants.

Thus the blood-root, with its red juice, was supposed to be useful in

blood diseases, in stopping hemorrhage, or in subduing the redness of an

inflammation.

Paracelsus's system of signatures, however, was so complicated by

his theories of astronomy and alchemy that it is practically beyond

comprehension. It is possible that he himself may have understood it,

but it is improbable that any one else did--as shown by the endless

discussions that have taken place about it. But with all the vagaries of

his theories he was still rational in his applications, and he attacked

to good purpose the complicated "shot-gun" prescriptions of his

contemporaries, advocating more simple methods of treatment.

The ever-fascinating subject of electricity, or, more specifically,

"magnetism," found great favor with him, and with properly adjusted

magnets he claimed to be able to cure many diseases. In epilepsy

and lockjaw, for example, one had but to fasten magnets to the four

extremities of the body, and then, "when the proper medicines were

given," the cure would be effected. The easy loop-hole for excusing

failure on the ground of improper medicines is obvious, but Paracelsus

declares that this one prescription is of more value than "all the

humoralists have ever written or taught."

Since Paracelsus condemned the study of anatomy as useless, he quite

naturally regarded surgery in the same light. In this he would have done

far better to have studied some of his predecessors, such as Galen,

Paul of Aegina, and Avicenna. But instead of "cutting men to pieces," he

taught that surgeons would gain more by devoting their time to searching

for the universal panacea which would cure all diseases, surgical as

well as medical. In this we detect a taint of the popular belief in the

philosopher's stone and the magic elixir of life, his belief in which

have been stoutly denied by some of his followers. He did admit,

however, that one operation alone was perhaps permissible--lithotomy, or

the "cutting for stone."

His influence upon medicine rests undoubtedly upon his revolutionary

attitude, rather than on any great or new discoveries made by him. It is

claimed by many that he brought prominently into use opium and mercury,

and if this were indisputably proven his services to medicine could

hardly be overestimated. Unfortunately, however, there are good grounds

for doubting that he was particularly influential in reintroducing these

medicines. His chief influence may perhaps be summed up in a single

phrase--he overthrew old traditions.

To Paracelsus's endeavors, however, if not to the actual products of his

work, is due the credit of setting in motion the chain of thought that

developed finally into scientific chemistry. Nor can the ultimate aim

of the modern chemist seek a higher object than that of this

sixteenth-century alchemist, who taught that "true alchemy has but one

aim and object, to extract the quintessence of things, and to prepare

arcana, tinctures, and elixirs which may restore to man the health and

soundness he has lost."

THE GREAT ANATOMISTS

About the beginning of the sixteenth century, while Paracelsus was

scoffing at the study of anatomy as useless, and using his influence

against it, there had already come upon the scene the first of the great

anatomists whose work was to make the century conspicuous in that branch

of medicine.

The young anatomist Charles etienne (1503-1564) made one of the first

noteworthy discoveries, pointing out for the first time that the spinal

cord contains a canal, continuous throughout its length. He also made

other minor discoveries of some importance, but his researches were

completely overshadowed and obscured by the work of a young Fleming

who came upon the scene a few years later, and who shone with such

brilliancy in the medical world that he obscured completely the work of

his contemporary until many years later. This young physician, who was

destined to lead such an eventful career and meet such an untimely end

as a martyr to science, was Andrew Vesalius (1514-1564), who is called

the "greatest of anatomists." At the time he came into the field

medicine was struggling against the dominating Galenic teachings and

the theories of Paracelsus, but perhaps most of all against the

superstitions of the time. In France human dissections were attended

with such dangers that the young Vesalius transferred his field of

labors to Italy, where such investigations were covertly permitted, if

not openly countenanced.

From the very start the young Fleming looked askance at the accepted

teachings of the day, and began a series of independent investigations

based upon his own observations. The results of these investigations

he gave in a treatise on the subject which is regarded as the first

comprehensive and systematic work on human anatomy. This remarkable work

was published in the author's twenty-eighth or twenty-ninth year. Soon

after this Vesalius was invited as imperial physician to the court of

Emperor Charles V. He continued to act in the same capacity at the court

of Philip II., after the abdication of his patron. But in spite of this

royal favor there was at work a factor more powerful than the influence

of the monarch himself--an instrument that did so much to retard

scientific progress, and by which so many lives were brought to a

premature close.

Vesalius had received permission from the kinsmen of a certain grandee

to perform an autopsy. While making his observations the heart of the

outraged body was seen to palpitate--so at least it was reported. This

was brought immediately to the attention of the Inquisition, and it was

only by the intervention of the king himself that the anatomist escaped

the usual fate of those accused by that tribunal. As it was, he was

obliged to perform a pilgrimage to the Holy Land. While returning from

this he was shipwrecked, and perished from hunger and exposure on the

island of Zante.

At the very time when the anatomical writings of Vesalius were startling

the medical world, there was living and working contemporaneously

another great anatomist, Eustachius (died 1574), whose records of his

anatomical investigations were ready for publication only nine years

after the publication of the work of Vesalius. Owing to the unfortunate

circumstances of the anatomist, however, they were never published

during his lifetime--not, in fact, until 1714. When at last they were

given to the world as Anatomical Engravings, they showed conclusively

that Eustachius was equal, if not superior to Vesalius in his knowledge

of anatomy. It has been said of this remarkable collection of engravings

that if they had been published when they were made in the sixteenth

century, anatomy would have been advanced by at least two centuries.

But be this as it may, they certainly show that their author was a most

careful dissector and observer.

Eustachius described accurately for the first time certain structures

of the middle ear, and rediscovered the tube leading from the ear to the

throat that bears his name. He also made careful studies of the teeth

and the phenomena of first and second dentition. He was not baffled by

the minuteness of structures and where he was unable to study them

with the naked eye he used glasses for the purpose, and resorted

to macerations and injections for the study of certain complicated

structures. But while the fruit of his pen and pencil were lost for more

than a century after his death, the effects of his teachings were not;

and his two pupils, Fallopius and Columbus, are almost as well known

to-day as their illustrious teacher. Columbus (1490-1559) did much in

correcting the mistakes made in the anatomy of the bones as described by

Vesalius. He also added much to the science by giving correct accounts

of the shape and cavities of the heart, and made many other discoveries

of minor importance. Fallopius (1523-1562) added considerably to the

general knowledge of anatomy, made several discoveries in the anatomy of

the ear, and also several organs in the abdominal cavity.

At this time a most vitally important controversy was in progress as to

whether or not the veins of the bodies were supplied with valves, many

anatomists being unable to find them. Etienne had first described these

structures, and Vesalius had confirmed his observations. It would seem

as if there could be no difficulty in settling the question as to the

fact of such valves being present in the vessels, for the demonstration

is so simple that it is now made daily by medical students in all

physiological laboratories and dissecting-rooms. But many of the

great anatomists of the sixteenth century were unable to make this

demonstration, even when it had been brought to their attention by such

an authority as Vesalius. Fallopius, writing to Vesalius on the subject

in 1562, declared that he was unable to find such valves. Others,

however, such as Eustachius and Fabricius (1537-1619), were more

successful, and found and described these structures. But the purpose

served by these valves was entirely misinterpreted. That they act in

preventing the backward flow of the blood in the veins on its way to the

heart, just as the valves of the heart itself prevent regurgitation, has

been known since the time of Harvey; but the best interpretation that

could be given at that time, even by such a man as Fabricius, was that

they acted in retarding the flow of the blood as it comes from the

heart, and thus prevent its too rapid distribution throughout the body.

The fact that the blood might have been going towards the heart, instead

of coming from it, seems never to have been considered seriously until

demonstrated so conclusively by Harvey.

Of this important and remarkable controversy over the valves in veins,

Withington has this to say: "This is truly a marvellous story. A great

Galenic anatomist is first to give a full and correct description of the

valves and their function, but fails to see that any modification of the

old view as to the motion of the blood is required. Two able dissectors

carefully test their action by experiment, and come to a result, the

exact reverse of the truth. Urged by them, the two foremost anatomists

of the age make a special search for valves and fail to find them.

Finally, passing over lesser peculiarities, an aged and honorable

professor, who has lived through all this, calmly asserts that no

anatomist, ancient or modern, has ever mentioned valves in veins till he

discovered them in 1574!"(2)

Among the anatomists who probably discovered these valves was Michael

Servetus (1511-1553); but if this is somewhat in doubt, it is certain

that he discovered and described the pulmonary circulation, and had

a very clear idea of the process of respiration as carried on in the

lungs. The description was contained in a famous document sent to Calvin

in 1545--a document which the reformer carefully kept for seven years

in order that he might make use of some of the heretical statements it

contained to accomplish his desire of bringing its writer to the stake.

The awful fate of Servetus, the interesting character of the man, and

the fact that he came so near to anticipating the discoveries of Harvey

make him one of the most interesting figures in medical history.

In this document which was sent to Calvin, Servetus rejected the

doctrine of natural, vital, and animal spirits, as contained in the

veins, arteries, and nerves respectively, and made the all-important

statement that the fluids contained in veins and arteries are the same.

He showed also that the blood is "purged from fume" and purified by

respiration in the lungs, and declared that there is a new vessel in the

lungs, "formed out of vein and artery." Even at the present day there is

little to add to or change in this description of Servetus's.

By keeping this document, pregnant with advanced scientific views, from

the world, and in the end only using it as a means of destroying

its author, the great reformer showed the same jealousy in retarding

scientific progress as had his arch-enemies of the Inquisition, at whose

dictates Vesalius became a martyr to science, and in whose dungeons

etienne perished.

THE COMING OF HARVEY

The time was ripe for the culminating discovery of the circulation of

the blood; but as yet no one had determined the all-important fact that

there are two currents of blood in the body, one going to the heart, one

coming from it. The valves in the veins would seem to show conclusively

that the venous current did not come from the heart, and surgeons must

have observed thousands of times the every-day phenomenon of congested

veins at the distal extremity of a limb around which a ligature or

constriction of any kind had been placed, and the simultaneous depletion

of the vessels at the proximal points above the ligature. But it should

be remembered that inductive science was in its infancy. This was the

sixteenth, not the nineteenth century, and few men had learned to put

implicit confidence in their observations and convictions when opposed

to existing doctrines. The time was at hand, however, when such a man

was to make his appearance, and, as in the case of so many revolutionary

doctrines in science, this man was an Englishman. It remained for

William Harvey (1578-1657) to solve the great mystery which had puzzled

the medical world since the beginning of history; not only to solve it,

but to prove his case so conclusively and so simply that for all time

his little booklet must he handed down as one of the great masterpieces

of lucid and almost faultless demonstration.

Harvey, the son of a prosperous Kentish yeoman, was born at Folkestone.

His education was begun at the grammar-school of Canterbury, and later

he became a pensioner of Caius College, Cambridge. Soon after taking his

degree of B.A., at the age of nineteen, he decided upon the profession

of medicine, and went to Padua as a pupil of Fabricius and Casserius.

Returning to England at the age of twenty-four, he soon after (1609)

obtained the reversion of the post of physician to St. Bartholomew's

Hospital, his application being supported by James I. himself. Even at

this time he was a popular physician, counting among his patients such

men as Francis Bacon. In 1618 he was appointed physician extraordinary

to the king, and, a little later, physician in ordinary. He was in

attendance upon Charles I. at the battle of Edgehill, in 1642, where,

with the young Prince of Wales and the Duke of York, after seeking

shelter under a hedge, he drew a book out of his pocket and, forgetful

of the battle, became absorbed in study, until finally the cannon-balls

from the enemy's artillery made him seek a more sheltered position.

On the fall of Charles I. he retired from practice, and lived in

retirement with his brother. He was then well along in years, but

still pursued his scientific researches with the same vigor as before,

directing his attention chiefly to the study of embryology. On June 3,

1657, he was attacked by paralysis and died, in his eightieth year. He

had lived to see his theory of the circulation accepted, several years

before, by all the eminent anatomists of the civilized world.

A keenness in the observation of facts, characteristic of the mind of

the man, had led Harvey to doubt the truth of existing doctrines as to

the phenomena of the circulation. Galen had taught that "the arteries

are filled, like bellows, because they are expanded," but Harvey thought

that the action of spurting blood from a severed vessel disproved

this. For the spurting was remittant, "now with greater, now with less

impetus," and its greater force always corresponded to the expansion

(diastole), not the contraction (systole) of the vessel. Furthermore,

it was evident that contraction of the heart and the arteries was not

simultaneous, as was commonly taught, because in that case there would

be no marked propulsion of the blood in any direction; and there was no

gainsaying the fact that the blood was forcibly propelled in a definite

direction, and that direction away from the heart.

Harvey's investigations led him to doubt also the accepted theory

that there was a porosity in the septum of tissue that divides the two

ventricles of the heart. It seemed unreasonable to suppose that a thick

fluid like the blood could find its way through pores so small that they

could not be demonstrated by any means devised by man. In evidence

that there could be no such openings he pointed out that, since the two

ventricles contract at the same time, this process would impede rather

than facilitate such an intra-ventricular passage of blood. But what

seemed the most conclusive proof of all was the fact that in the foetus

there existed a demonstrable opening between the two ventricles, and yet

this is closed in the fully developed heart. Why should Nature, if she

intended that blood should pass between the two cavities, choose to

close this opening and substitute microscopic openings in place of it?

It would surely seem more reasonable to have the small perforations in

the thin, easily permeable membrane of the foetus, and the opening in

the adult heart, rather than the reverse. From all this Harvey drew his

correct conclusions, declaring earnestly, "By Hercules, there ARE no

such porosities, and they cannot be demonstrated."

Having convinced himself that no intra-ventricular opening existed, he

proceeded to study the action of the heart itself, untrammelled by too

much faith in established theories, and, as yet, with no theory of his

own. He soon discovered that the commonly accepted theory of the heart

striking against the chest-wall during the period of relaxation was

entirely wrong, and that its action was exactly the reverse of this, the

heart striking the chest-wall during contraction. Having thus disproved

the accepted theory concerning the heart's action, he took up the

subject of the action of arteries, and soon was able to demonstrate by

vivisection that the contraction of the arteries was not simultaneous

with contractions of the heart. His experiments demonstrated that these

vessels were simply elastic tubes whose pulsations were "nothing else

than the impulse of the blood within them." The reason that the arterial

pulsation was not simultaneous with the heart-beat he found to be

because of the time required to carry the impulse along the tube.

By a series of further careful examinations and experiments, which are

too extended to be given here, he was soon able further to demonstrate

the action and course of the blood during the contractions of the heart.

His explanations were practically the same as those given to-day--first

the contraction of the auricle, sending blood into the ventricle; then

ventricular contraction, making the pulse, and sending the blood into

the arteries. He had thus demonstrated what had not been generally

accepted before, that the heart was an organ for the propulsion of

blood. To make such a statement to-day seems not unlike the sober

announcement that the earth is round or that the sun does not revolve

about it. Before Harvey's time, however, it was considered as an organ

that was "in some mysterious way the source of vitality and warmth, as

an animated crucible for the concoction of blood and the generation of

vital spirits."(3)

In watching the rapid and ceaseless contractions of the heart, Harvey

was impressed with the fact that, even if a very small amount of blood

was sent out at each pulsation, an enormous quantity must pass through

the organ in a day, or even in an hour. Estimating the size of the

cavities of the heart, and noting that at least a drachm must be sent

out with each pulsation, it was evident that the two thousand beats

given by a very slow human heart in an hour must send out some forty

pounds of blood--more than twice the amount in the entire body. The

question was, what became of it all? For it should be remembered that

the return of the blood by the veins was unknown, and nothing like a

"circulation" more than vaguely conceived even by Harvey himself. Once

it could be shown that the veins were constantly returning blood to the

heart, the discovery that the blood in some way passes from the arteries

to the veins was only a short step. Harvey, by resorting to vivisections

of lower animals and reptiles, soon demonstrated beyond question the

fact that the veins do carry the return blood. "But this, in particular,

can be shown clearer than daylight," says Harvey. "The vena cava enters

the heart at an inferior portion, while the artery passes out above. Now

if the vena cava be taken up with forceps or the thumb and finger, and

the course of the blood intercepted for some distance below the heart,

you will at once see it almost emptied between the fingers and the

heart, the blood being exhausted by the heart's pulsation, the heart

at the same time becoming much paler even in its dilatation, smaller

in size, owing to the deficiency of blood, and at length languid in

pulsation, as if about to die. On the other hand, when you release the

vein the heart immediately regains its color and dimensions. After that,

if you leave the vein free and tie and compress the arteries at some

distance from the heart, you will see, on the contrary, their included

portion grow excessively turgid, the heart becoming so beyond measure,

assuming a dark-red color, even to lividity, and at length so overloaded

with blood as to seem in danger of suffocation; but when the obstruction

is removed it returns to its normal condition, in size, color, and

movement."(4)

This conclusive demonstration that the veins return the blood to the

heart must have been most impressive to Harvey, who had been taught to

believe that the blood current in the veins pursued an opposite course,

and must have tended to shake his faith in all existing doctrines of the

day.

His next step was the natural one of demonstrating that the blood passes

from the arteries to the veins. He demonstrated conclusively that this

did occur, but for once his rejection of the ancient writers and one

modern one was a mistake. For Galen had taught, and had attempted

to demonstrate, that there are sets of minute vessels connecting the

arteries and the veins; and Servetus had shown that there must be such

vessels, at least in the lungs.

However, the little flaw in the otherwise complete demonstration of

Harvey detracts nothing from the main issue at stake. It was for others

who followed to show just how these small vessels acted in effecting

the transfer of the blood from artery to vein, and the grand general

statement that such a transfer does take place was, after all, the

all-important one, and the exact method of how it takes place a detail.

Harvey's experiments to demonstrate that the blood passes from the

arteries to the veins are so simply and concisely stated that they may

best be given in his own words.

"I have here to cite certain experiments," he wrote, "from which it

seems obvious that the blood enters a limb by the arteries, and returns

from it by the veins; that the arteries are the vessels carrying the

blood from the heart, and the veins the returning channels of the blood

to the heart; that in the limbs and extreme parts of the body the

blood passes either by anastomosis from the arteries into the veins, or

immediately by the pores of the flesh, or in both ways, as has already

been said in speaking of the passage of the blood through the lungs;

whence it appears manifest that in the circuit the blood moves from

thence hither, and hence thither; from the centre to the extremities, to

wit, and from the extreme parts back again to the centre. Finally, upon

grounds of circulation, with the same elements as before, it will be

obvious that the quantity can neither be accounted for by the ingesta,

nor yet be held necessary to nutrition.

"Now let any one make an experiment on the arm of a man, either using

such a fillet as is employed in blood-letting or grasping the limb

tightly with his hand, the best subject for it being one who is lean,

and who has large veins, and the best time after exercise, when the body

is warm, the pulse is full, and the blood carried in large quantities

to the extremities, for all then is more conspicuous; under such

circumstances let a ligature be thrown about the extremity and drawn

as tightly as can be borne: it will first be perceived that beyond the

ligature neither in the wrist nor anywhere else do the arteries pulsate,

that at the same time immediately above the ligature the artery begins

to rise higher at each diastole, to throb more violently, and to swell

in its vicinity with a kind of tide, as if it strove to break through

and overcome the obstacle to its current; the artery here, in

short, appears as if it were permanently full. The hand under such

circumstances retains its natural color and appearances; in the course

of time it begins to fall somewhat in temperature, indeed, but nothing

is DRAWN into it.

"After the bandage has been kept on some short time in this way, let

it be slackened a little, brought to the state or term of middling

tightness which is used in bleeding, and it will be seen that the

whole hand and arm will instantly become deeply suffused and distended,

injected, gorged with blood, DRAWN, as it is said, by this middling

ligature, without pain, or heat, or any horror of a vacuum, or any other

cause yet indicated.

"As we have noted, in connection with the tight ligature, that the

artery above the bandage was distended and pulsated, not below it, so,

in the case of the moderately tight bandage, on the contrary, do we find

that the veins below, never above, the fillet swell and become dilated,

while the arteries shrink; and such is the degree of distention of the

veins here that it is only very strong pressure that will force the

blood beyond the fillet and cause any of the veins in the upper part of

the arm to rise.

"From these facts it is easy for any careful observer to learn that the

blood enters an extremity by the arteries; for when they are effectively

compressed nothing is DRAWN to the member; the hand preserves its color;

nothing flows into it, neither is it distended; but when the pressure is

diminished, as it is with the bleeding fillet, it is manifest that the

blood is instantly thrown in with force, for then the hand begins to

swell; which is as much as to say that when the arteries pulsate the

blood is flowing through them, as it is when the moderately tight

ligature is applied; but when they do not pulsate, or when a tight

ligature is used, they cease from transmitting anything; they are only

distended above the part where the ligature is applied. The veins again

being compressed, nothing can flow through them; the certain indication

of which is that below the ligature they are much more tumid than above

it, and than they usually appear when there is no bandage upon the arm.

"It therefore plainly appears that the ligature prevents the return of

the blood through the veins to the parts above it, and maintains those

beneath it in a state of permanent distention. But the arteries, in

spite of the pressure, and under the force and impulse of the heart,

send on the blood from the internal parts of the body to the parts

beyond the bandage."(5)

This use of ligatures is very significant, because, as shown, a very

tight ligature stops circulation in both arteries and veins, while a

loose one, while checking the circulation in the veins, which lie nearer

the surface and are not so directly influenced by the force of the

heart, does not stop the passage of blood in the arteries, which are

usually deeply imbedded in the tissues, and not so easily influenced by

pressure from without.

The last step of Harvey's demonstration was to prove that the blood does

flow along the veins to the heart, aided by the valves that had been

the cause of so much discussion and dispute between the great

sixteenth-century anatomists. Harvey not only demonstrated the presence

of these valves, but showed conclusively, by simple experiments, what

their function was, thus completing his demonstration of the phenomena

of the circulation.

The final ocular demonstration of the passage of the blood from the

arteries to the veins was not to be made until four years after Harvey's

death. This process, which can be observed easily in the web of a frog's

foot by the aid of a low-power lens, was first demonstrated by Marcello

Malpighi (1628-1694) in 1661. By the aid of a lens he first saw the

small "capillary" vessels connecting the veins and arteries in a piece

of dried lung. Taking his cue from this, he examined the lung of a

turtle, and was able to see in it the passage of the corpuscles through

these minute vessels, making their way along these previously unknown

channels from the arteries into the veins on their journey back to the

heart. Thus the work of Harvey, all but complete, was made absolutely

entire by the great Italian. And all this in a single generation.

LEEUWENHOEK DISCOVERS BACTERIA

The seventeenth century was not to close, however, without another

discovery in science, which, when applied to the causation of disease

almost two centuries later, revolutionized therapeutics more completely

than any one discovery. This was the discovery of microbes, by Antonius

von Leeuwenhoek (1632-1723), in 1683. Von Leeuwenhoek discovered

that "in the white matter between his teeth" there were millions of

microscopic "animals"--more, in fact, than "there were human beings in

the united Netherlands," and all "moving in the most delightful manner."

There can be no question that he saw them, for we can recognize in

his descriptions of these various forms of little "animals" the four

principal forms of microbes--the long and short rods of bacilli and

bacteria, the spheres of micrococci, and the corkscrew spirillum.

The presence of these microbes in his mouth greatly annoyed Antonius,

and he tried various methods of getting rid of them, such as using

vinegar and hot coffee. In doing this he little suspected that he was

anticipating modern antiseptic surgery by a century and three-quarters,

and to be attempting what antiseptic surgery is now able to accomplish.

For the fundamental principle of antisepsis is the use of medicines for

ridding wounds of similar microscopic organisms. Von Leenwenhoek was

only temporarily successful in his attempts, however, and took occasion

to communicate his discovery to the Royal Society of England, hoping

that they would be "interested in this novelty." Probably they were,

but not sufficiently so for any member to pursue any protracted

investigations or reach any satisfactory conclusions, and the whole

matter was practically forgotten until the middle of the nineteenth

century.

VIII. MEDICINE IN THE SIXTEENTH AND SEVENTEENTH CENTURIES

Of the half-dozen surgeons who were prominent in the sixteenth century,

Ambroise Pare (1517-1590), called the father of French surgery, is

perhaps the most widely known. He rose from the position of a common

barber to that of surgeon to three French monarchs, Henry II., Francis

II., and Charles IX. Some of his mottoes are still first principles of

the medical man. Among others are: "He who becomes a surgeon for the

sake of money, and not for the sake of knowledge, will accomplish

nothing"; and "A tried remedy is better than a newly invented." On his

statue is his modest estimate of his work in caring for the wounded, "Je

le pansay, Dieu le guarit"--I dressed him, God cured him.

It was in this dressing of wounds on the battlefield that he

accidentally discovered how useless and harmful was the terribly painful

treatment of applying boiling oil to gunshot wounds as advocated by John

of Vigo. It happened that after a certain battle, where there was an

unusually large number of casualties, Pare found, to his horror, that no

more boiling oil was available for the surgeons, and that he should be

obliged to dress the wounded by other simpler methods. To his amazement

the results proved entirely satisfactory, and from that day he discarded

the hot-oil treatment.

As Pare did not understand Latin he wrote his treatises in French, thus

inaugurating a custom in France that was begun by Paracelsus in Germany

half a century before. He reintroduced the use of the ligature in

controlling hemorrhage, introduced the "figure of eight" suture in the

operation for hare-lip, improved many of the medico-legal doctrines, and

advanced the practice of surgery generally. He is credited with having

successfully performed the operation for strangulated hernia, but he

probably borrowed it from Peter Franco (1505-1570), who published an

account of this operation in 1556. As this operation is considered by

some the most important operation in surgery, its discoverer is entitled

to more than passing notice, although he was despised and ignored by the

surgeons of his time.

Franco was an illiterate travelling lithotomist--a class of itinerant

physicians who were very generally frowned down by the regular

practitioners of medicine. But Franco possessed such skill as an

operator, and appears to have been so earnest in the pursuit of what he

considered a legitimate calling, that he finally overcame the popular

prejudice and became one of the salaried surgeons of the republic of

Bern. He was the first surgeon to perform the suprapubic lithotomy

operation--the removal of stone through the abdomen instead of through

the perineum. His works, while written in an illiterate style, give the

clearest descriptions of any of the early modern writers.

As the fame of Franco rests upon his operation for prolonging human

life, so the fame of his Italian contemporary, Gaspar Tagliacozzi

(1545-1599), rests upon his operation for increasing human comfort and

happiness by restoring amputated noses. At the time in which he lived

amputation of the nose was very common, partly from disease, but also

because a certain pope had fixed the amputation of that member as the

penalty for larceny. Tagliacozzi probably borrowed his operation

from the East; but he was the first Western surgeon to perform it and

describe it. So great was the fame of his operations that patients

flocked to him from all over Europe, and each "went away with as many

noses as he liked." Naturally, the man who directed his efforts to

restoring structures that bad been removed by order of the Church was

regarded in the light of a heretic by many theologians; and though he

succeeded in cheating the stake or dungeon, and died a natural death,

his body was finally cast out of the church in which it had been buried.

In the sixteenth century Germany produced a surgeon, Fabricius Hildanes

(1560-1639), whose work compares favorably with that of Pare, and

whose name would undoubtedly have been much better known had not the

circumstances of the time in which he lived tended to obscure his

merits. The blind followers of Paracelsus could see nothing outside the

pale of their master's teachings, and the disastrous Thirty Years' War

tended to obscure and retard all scientific advances in Germany. Unlike

many of his fellow-surgeons, Hildanes was well versed in Latin and

Greek; and, contrary to the teachings of Paracelsus, he laid particular

stress upon the necessity of the surgeon having a thorough knowledge

of anatomy. He had a helpmate in his wife, who was also something of a

surgeon, and she is credited with having first made use of the magnet

in removing particles of metal from the eye. Hildanes tells of a certain

man who had been injured by a small piece of steel in the cornea,

which resisted all his efforts to remove it. After observing Hildanes'

fruitless efforts for a time, it suddenly occurred to his wife to

attempt to make the extraction with a piece of loadstone. While the

physician held open the two lids, his wife attempted to withdraw the

steel with the magnet held close to the cornea, and after several

efforts she was successful--which Hildanes enumerates as one of the

advantages of being a married man.

Hildanes was particularly happy in his inventions of surgical

instruments, many of which were designed for locating and removing the

various missiles recently introduced in warfare.

The seventeenth century, which was such a flourishing one for anatomy

and physiology, was not as productive of great surgeons or advances in

surgery as the sixteenth had been or the eighteenth was to be. There was

a gradual improvement all along the line, however, and much of the work

begun by such surgeons as Pare and Hildanes was perfected or improved.

Perhaps the most progressive surgeon of the century was an Englishman,

Richard Wiseman (1625-1686), who, like Harvey, enjoyed royal favor,

being in the service of all the Stuart kings. He was the first surgeon

to advocate primary amputation, in gunshot wounds, of the limbs, and

also to introduce the treatment of aneurisms by compression; but he

is generally rated as a conservative operator, who favored medication

rather than radical operations, where possible.

In Italy, Marcus Aurelius Severinus (1580-1656) and Peter Marchettis

(1589-1675) were the leading surgeons of their nation. Like many of his

predecessors in Europe, Severinus ran amuck with the Holy Inquisition

and fled from Naples. But the waning of the powerful arm of the Church

is shown by the fact that he was brought back by the unanimous voice

of the grateful citizens, and lived in safety despite the frowns of the

theologians.

The sixteenth century cannot be said to have added much of importance in

the field of practical medicine, and, as in the preceding and succeeding

centuries, was at best only struggling along in the wake of anatomy,

physiology, and surgery. In the seventeenth century, however, at least

one discovery in therapeutics was made that has been an inestimable boon

to humanity ever since. This was the introduction of cinchona bark (from

which quinine is obtained) in 1640. But this century was productive

of many medical SYSTEMS, and could boast of many great names among the

medical profession, and, on the whole, made considerably more progress

than the preceding century.

Of the founders of medical systems, one of the most widely known is Jan

Baptista van Helmont (1578-1644), an eccentric genius who constructed

a system of medicine of his own and for a time exerted considerable

influence. But in the end his system was destined to pass out of

existence, not very long after the death of its author. Van Helmont

was not only a physician, but was master of all the other branches of

learning of the time, taking up the study of medicine and chemistry

as an after-thought, but devoting himself to them with the greatest

enthusiasm once he had begun his investigations. His attitude towards

existing doctrines was as revolutionary as that of Paracelsus, and he

rejected the teachings of Galen and all the ancient writers, although

retaining some of the views of Paracelsus. He modified the archaeus of

Paracelsus, and added many complications to it. He believed the whole

body to be controlled by an archaeus influus, the soul by the archaei

insiti, and these in turn controlled by the central archeus. His system

is too elaborate and complicated for full explanation, but its chief

service to medicine was in introducing new chemical methods in the

preparation of drugs. In this way he was indirectly connected with the

establishment of the Iatrochemical school. It was he who first used the

word "gas"--a word coined by him, along with many others that soon fell

into disuse.

The principles of the Iatrochemical school were the use of chemical

medicines, and a theory of pathology different from the prevailing

"humoral" pathology. The founder of this school was Sylvius (Franz de

le Boe, 1614-1672), professor of medicine at Leyden. He attempted to

establish a permanent system of medicine based on the newly discovered

theory of the circulation and the new chemistry, but his name is

remembered by medical men because of the fissure in the brain (fissure

of Sylvius) that bears it. He laid great stress on the cause of fevers

and other diseases as originating in the disturbances of the process of

fermentation in the stomach. The doctrines of Sylvius spread widely over

the continent, but were not generally accepted in England until modified

by Thomas Willis (1622-1675), whose name, like that of Sylvius, is

perpetuated by a structure in the brain named after him, the circle

of Willis. Willis's descriptions of certain nervous diseases, and an

account of diabetes, are the first recorded, and added materially to

scientific medicine. These schools of medicine lasted until the end of

the seventeenth century, when they were finally overthrown by Sydenham.

The Iatrophysical school (also called iatromathematical,

iatromechanical, or physiatric) was founded on theories of physiology,

probably by Borelli, of Naples (1608-1679), although Sanctorius;

Sanctorius, a professor at Padua, was a precursor, if not directly

interested in establishing it. Sanctorius discovered the fact that an

"insensible perspiration" is being given off by the body continually,

and was amazed to find that loss of weight in this way far exceeded the

loss of weight by all other excretions of the body combined. He made

this discovery by means of a peculiar weighing-machine to which a chair

was attached, and in which he spent most of his time. Very naturally

he overestimated the importance of this discovery, but it was,

nevertheless, of great value in pointing out the hygienic importance

of the care of the skin. He also introduced a thermometer which he

advocated as valuable in cases of fever, but the instrument was probably

not his own invention, but borrowed from his friend Galileo.

Harvey's discovery of the circulation of the blood laid the foundation

of the Iatrophysical school by showing that this vital process was

comparable to a hydraulic system. In his On the Motive of Animals,

Borelli first attempted to account for the phenomena of life and

diseases on these principles. The iatromechanics held that the great

cause of disease is due to different states of elasticity of the solids

of the body interfering with the movements of the fluids, which

are themselves subject to changes in density, one or both of these

conditions continuing to cause stagnation or congestion. The school thus

founded by Borelli was the outcome of the unbounded enthusiasm, with its

accompanying exaggeration of certain phenomena with the corresponding

belittling of others that naturally follows such a revolutionary

discovery as that of Harvey. Having such a founder as the brilliant

Italian Borelli, it was given a sufficient impetus by his writings

to carry it some distance before it finally collapsed. Some of the

exaggerated mathematical calculations of Borelli himself are worth

noting. Each heart-beat, as he calculated it, overcomes a resistance

equal to one hundred and eighty thousand pounds;--the modern

physiologist estimates its force at from five to nine ounces!

THOMAS SYDENHAM

But while the Continent was struggling with these illusive "systems,"

and dabbling in mystic theories that were to scarcely outlive the men

who conceived them, there appeared in England--the "land of

common-sense," as a German scientist has called it--"a cool, clear, and

unprejudiced spirit," who in the golden age of systems declined "to be

like the man who builds the chambers of the upper story of his house

before he had laid securely the foundation walls."(1) This man was

Thomas Sydenham (1624-1689), who, while the great Harvey was serving the

king as surgeon, was fighting as a captain in the parliamentary army.

Sydenham took for his guide the teachings of Hippocrates, modified to

suit the advances that had been made in scientific knowledge since the

days of the great Greek, and established, as a standard, observation and

experience. He cared little for theory unless confirmed by practice, but

took the Hippocratic view that nature cured diseases, assisted by the

physician. He gave due credit, however, to the importance of the part

played by the assistant. As he saw it, medicine could be advanced in

three ways: (1) "By accurate descriptions or natural histories of

diseases; (2) by establishing a fixed principle or method of treatment,

founded upon experience; (3) by searching for specific remedies, which

he believes must exist in considerable numbers, though he admits that

the only one yet discovered is Peruvian bark."(2) As it happened,

another equally specific remedy, mercury, when used in certain diseases,

was already known to him, but he evidently did not recognize it as such.

The influence on future medicine of Sydenham's teachings was most

pronounced, due mostly to his teaching of careful observation. To most

physicians, however, he is now remembered chiefly for his introduction

of the use of laudanum, still considered one of the most valuable

remedies of modern pharmacopoeias. The German gives the honor of

introducing this preparation to Paracelsus, but the English-speaking

world will always believe that the credit should be given to Sydenham.

IX. PHILOSOPHER-SCIENTISTS AND NEW INSTITUTIONS OF LEARNING

We saw that in the old Greek days there was no sharp line of demarcation

between the field of the philosopher and that of the scientist. In the

Hellenistic epoch, however, knowledge became more specialized, and our

recent chapters have shown us scientific investigators whose efforts

were far enough removed from the intangibilities of the philosopher. It

must not be overlooked, however, that even in the present epoch there

were men whose intellectual efforts were primarily directed towards

the subtleties of philosophy, yet who had also a penchant for

strictly scientific imaginings, if not indeed for practical scientific

experiments. At least three of these men were of sufficient importance

in the history of the development of science to demand more than passing

notice. These three are the Englishman Francis Bacon (1561-1626), the

Frenchman Rene Descartes (1596-1650); and the German Gottfried Leibnitz

(1646-1716). Bacon, as the earliest path-breaker, showed the way,

theoretically at least, in which the sciences should be studied;

Descartes, pursuing the methods pointed out by Bacon, carried the same

line of abstract reason into practice as well; while Leibnitz, coming

some years later, and having the advantage of the wisdom of his two

great predecessors, was naturally influenced by both in his views of

abstract scientific principles.

Bacon's career as a statesman and his faults and misfortunes as a man do

not concern us here. Our interest in him begins with his entrance

into Trinity College, Cambridge, where he took up the study of all the

sciences taught there at that time. During the three years he became

more and more convinced that science was not being studied in a

profitable manner, until at last, at the end of his college course, he

made ready to renounce the old Aristotelian methods of study and advance

his theory of inductive study. For although he was a great admirer of

Aristotle's work, he became convinced that his methods of approaching

study were entirely wrong.

"The opinion of Aristotle," he says, in his De Argumentum Scientiarum,

"seemeth to me a negligent opinion, that of those things which exist by

nature nothing can be changed by custom; using for example, that if a

stone be thrown ten thousand times up it will not learn to ascend; and

that by often seeing or hearing we do not learn to see or hear better.

For though this principle be true in things wherein nature is peremptory

(the reason whereof we cannot now stand to discuss), yet it is otherwise

in things wherein nature admitteth a latitude. For he might see that a

straight glove will come more easily on with use; and that a wand will

by use bend otherwise than it grew; and that by use of the voice we

speak louder and stronger; and that by use of enduring heat or cold

we endure it the better, and the like; which latter sort have a

nearer resemblance unto that subject of manners he handleth than those

instances which he allegeth."(1)

These were his opinions, formed while a young man in college, repeated

at intervals through his maturer years, and reiterated and emphasized in

his old age. Masses of facts were to be obtained by observing nature at

first hand, and from such accumulations of facts deductions were to be

made. In short, reasoning was to be from the specific to the general,

and not vice versa.

It was by his teachings alone that Bacon thus contributed to the

foundation of modern science; and, while he was constantly thinking

and writing on scientific subjects, he contributed little in the way of

actual discoveries. "I only sound the clarion," he said, "but I enter

not the battle."

The case of Descartes, however, is different. He both sounded the

clarion and entered into the fight. He himself freely acknowledges

his debt to Bacon for his teachings of inductive methods of study, but

modern criticism places his work on the same plane as that of the great

Englishman. "If you lay hold of any characteristic product of modern

ways of thinking," says Huxley, "either in the region of philosophy

or in that of science, you find the spirit of that thought, if not its

form, has been present in the mind of the great Frenchman."(2)

Descartes, the son of a noble family of France, was educated by Jesuit

teachers. Like Bacon, he very early conceived the idea that the methods

of teaching and studying science were wrong, but be pondered the

matter well into middle life before putting into writing his ideas of

philosophy and science. Then, in his Discourse Touching the Method of

Using One's Reason Rightly and of Seeking Scientific Truth, he pointed

out the way of seeking after truth. His central idea in this was to

emphasize the importance of DOUBT, and avoidance of accepting as truth

anything that does not admit of absolute and unqualified proof. In

reaching these conclusions he had before him the striking examples of

scientific deductions by Galileo, and more recently the discovery of the

circulation of the blood by Harvey. This last came as a revelation to

scientists, reducing this seemingly occult process, as it did, to the

field of mechanical phenomena. The same mechanical laws that governed

the heavenly bodies, as shown by Galileo, governed the action of the

human heart, and, for aught any one knew, every part of the body, and

even the mind itself.

Having once conceived this idea, Descartes began a series of dissections

and experiments upon the lower animals, to find, if possible, further

proof of this general law. To him the human body was simply a machine, a

complicated mechanism, whose functions were controlled just as any other

piece of machinery. He compared the human body to complicated machinery

run by water-falls and complicated pipes. "The nerves of the machine

which I am describing," he says, "may very well be compared to the pipes

of these waterworks; its muscles and its tendons to the other various

engines and springs which seem to move them; its animal spirits to the

water which impels them, of which the heart is the fountain; while the

cavities of the brain are the central office. Moreover, respiration

and other such actions as are natural and usual in the body, and which

depend on the course of the spirits, are like the movements of a clock,

or a mill, which may be kept up by the ordinary flow of water."(3)

In such passages as these Descartes anticipates the ideas of physiology

of the present time. He believed that the functions are performed by the

various organs of the bodies of animals and men as a mechanism, to which

in man was added the soul. This soul he located in the pineal gland, a

degenerate and presumably functionless little organ in the brain. For

years Descartes's idea of the function of this gland was held by many

physiologists, and it was only the introduction of modern high-power

microscopy that reduced this also to a mere mechanism, and showed that

it is apparently the remains of a Cyclopean eye once common to man's

remote ancestors.

Descartes was the originator of a theory of the movements of

the universe by a mechanical process--the Cartesian theory of

vortices--which for several decades after its promulgation reigned

supreme in science. It is the ingenuity of this theory, not the truth

of its assertions, that still excites admiration, for it has long since

been supplanted. It was certainly the best hitherto advanced--the best

"that the observations of the age admitted," according to D'Alembert.

According to this theory the infinite universe is full of matter, there

being no such thing as a vacuum. Matter, as Descartes believed, is

uniform in character throughout the entire universe, and since motion

cannot take place in any part of a space completely filled, without

simultaneous movement in all other parts, there are constant more or

less circular movements, vortices, or whirlpools of particles, varying,

of course, in size and velocity. As a result of this circular movement

the particles of matter tend to become globular from contact with one

another. Two species of matter are thus formed, one larger and globular,

which continue their circular motion with a constant tendency to fly

from the centre of the axis of rotation, the other composed of the

clippings resulting from the grinding process. These smaller "filings"

from the main bodies, becoming smaller and smaller, gradually lose their

velocity and accumulate in the centre of the vortex. This collection of

the smaller matter in the centre of the vortex constitutes the sun or

star, while the spherical particles propelled in straight lines from the

centre towards the circumference of the vortex produce the phenomenon

of light radiating from the central star. Thus this matter becomes the

atmosphere revolving around the accumulation at the centre. But the

small particles being constantly worn away from the revolving spherical

particles in the vortex, become entangled in their passage, and when

they reach the edge of the inner strata of solar dust they settle upon

it and form what we call sun-spots. These are constantly dissolved and

reformed, until sometimes they form a crust round the central nucleus.

As the expansive force of the star diminishes in the course of time,

it is encroached upon by neighboring vortices. If the part of the

encroaching star be of a less velocity than the star which it has swept

up, it will presently lose its hold, and the smaller star pass out of

range, becoming a comet. But if the velocity of the vortex into which

the incrusted star settles be equivalent to that of the surrounded

vortex, it will hold it as a captive, still revolving and "wrapt in its

own firmament." Thus the several planets of our solar system have

been captured and held by the sun-vortex, as have the moon and other

satellites.

But although these new theories at first created great enthusiasm among

all classes of philosophers and scientists, they soon came under the

ban of the Church. While no actual harm came to Descartes himself, his

writings were condemned by the Catholic and Protestant churches alike.

The spirit of philosophical inquiry he had engendered, however, lived

on, and is largely responsible for modern philosophy.

In many ways the life and works of Leibnitz remind us of Bacon rather

than Descartes. His life was spent in filling high political positions,

and his philosophical and scientific writings were by-paths of his

fertile mind. He was a theoretical rather than a practical scientist,

his contributions to science being in the nature of philosophical

reasonings rather than practical demonstrations. Had he been able

to withdraw from public life and devote himself to science alone, as

Descartes did, he would undoubtedly have proved himself equally great

as a practical worker. But during the time of his greatest activity in

philosophical fields, between the years 1690 and 1716, he was all the

time performing extraordinary active duties in entirely foreign fields.

His work may be regarded, perhaps, as doing for Germany in particular

what Bacon's did for England and the rest of the world in general.

Only a comparatively small part of his philosophical writings concern us

here. According to his theory of the ultimate elements of the universe,

the entire universe is composed of individual centres, or monads. To

these monads he ascribed numberless qualities by which every phase of

nature may be accounted. They were supposed by him to be percipient,

self-acting beings, not under arbitrary control of the deity, and

yet God himself was the original monad from which all the rest are

generated. With this conception as a basis, Leibnitz deduced his

doctrine of pre-established harmony, whereby the numerous independent

substances composing the world are made to form one universe. He

believed that by virtue of an inward energy monads develop themselves

spontaneously, each being independent of every other. In short, each

monad is a kind of deity in itself--a microcosm representing all the

great features of the macrocosm.

It would be impossible clearly to estimate the precise value of the

stimulative influence of these philosophers upon the scientific thought

of their time. There was one way, however, in which their influence was

made very tangible--namely, in the incentive they gave to the foundation

of scientific societies.

SCIENTIFIC SOCIETIES

At the present time, when the elements of time and distance are

practically eliminated in the propagation of news, and when cheap

printing has minimized the difficulties of publishing scientific

discoveries, it is difficult to understand the isolated position of

the scientific investigation of the ages that preceded steam and

electricity. Shut off from the world and completely out of touch with

fellow-laborers perhaps only a few miles away, the investigators were

naturally seriously handicapped; and inventions and discoveries were not

made with the same rapidity that they would undoubtedly have been had

the same men been receiving daily, weekly, or monthly communications

from fellow-laborers all over the world, as they do to-day. Neither did

they have the advantage of public or semi-public laboratories, where

they were brought into contact with other men, from whom to gather

fresh trains of thought and receive the stimulus of their successes or

failures. In the natural course of events, however, neighbors who were

interested in somewhat similar pursuits, not of the character of the

rivalry of trade or commerce, would meet more or less frequently and

discuss their progress. The mutual advantages of such intercourse would

be at once appreciated; and it would be but a short step from the

casual meeting of two neighborly scientists to the establishment of

"societies," meeting at fixed times, and composed of members living

within reasonable travelling distance. There would, perhaps, be the

weekly or monthly meetings of men in a limited area; and as the natural

outgrowth of these little local societies, with frequent meetings,

would come the formation of larger societies, meeting less often, where

members travelled a considerable distance to attend. And, finally,

with increased facilities for communication and travel, the great

international societies of to-day would be produced--the natural outcome

of the neighborly meetings of the primitive mediaeval investigators.

In Italy, at about the time of Galileo, several small societies were

formed. One of the most important of these was the Lyncean Society,

founded about the year 1611, Galileo himself being a member. This

society was succeeded by the Accademia del Cimento, at Florence, in

1657, which for a time flourished, with such a famous scientist as

Torricelli as one of its members.

In England an impetus seems to have been given by Sir Francis Bacon's

writings in criticism and censure of the system of teaching in

colleges. It is supposed that his suggestions as to what should be the

aims of a scientific society led eventually to the establishment of the

Royal Society. He pointed out how little had really been accomplished by

the existing institutions of learning in advancing science, and asserted

that little good could ever come from them while their methods of

teaching remained unchanged. He contended that the system which made

the lectures and exercises of such a nature that no deviation from the

established routine could be thought of was pernicious. But he showed

that if any teacher had the temerity to turn from the traditional paths,

the daring pioneer was likely to find insurmountable obstacles placed

in the way of his advancement. The studies were "imprisoned" within

the limits of a certain set of authors, and originality in thought or

teaching was to be neither contemplated nor tolerated.

The words of Bacon, given in strong and unsparing terms of censure and

condemnation, but nevertheless with perfect justification, soon bore

fruit. As early as the year 1645 a small company of scientists had been

in the habit of meeting at some place in London to discuss philosophical

and scientific subjects for mental advancement. In 1648, owing to

the political disturbances of the time, some of the members of these

meetings removed to Oxford, among them Boyle, Wallis, and Wren, where

the meetings were continued, as were also the meetings of those left in

London. In 1662, however, when the political situation bad become

more settled, these two bodies of men were united under a charter

from Charles II., and Bacon's ideas were practically expressed in that

learned body, the Royal Society of London. And it matters little that in

some respects Bacon's views were not followed in the practical workings

of the society, or that the division of labor in the early stages was

somewhat different than at present. The aim of the society has always

been one for the advancement of learning; and if Bacon himself could

look over its records, he would surely have little fault to find with

the aid it has given in carrying out his ideas for the promulgation of

useful knowledge.

Ten years after the charter was granted to the Royal Society of London,

Lord Bacon's words took practical effect in Germany, with the result

that the Academia Naturae Curiosorum was founded, under the leadership

of Professor J. C. Sturm. The early labors of this society were devoted

to a repetition of the most notable experiments of the time, and the

work of the embryo society was published in two volumes, in 1672 and

1685 respectively, which were practically text-books of the physics of

the period. It was not until 1700 that Frederick I. founded the Royal

Academy of Sciences at Berlin, after the elaborate plan of Leibnitz, who

was himself the first president.

Perhaps the nearest realization of Bacon's ideal, however, is in the

Royal Academy of Sciences at Paris, which was founded in 1666 under

the administration of Colbert, during the reign of Louis XIV. This

institution not only recognized independent members, but had besides

twenty pensionnaires who received salaries from the government. In

this way a select body of scientists were enabled to pursue their

investigations without being obliged to "give thought to the morrow"

for their sustenance. In return they were to furnish the meetings with

scientific memoirs, and once a year give an account of the work they

were engaged upon. Thus a certain number of the brightest minds

were encouraged to devote their entire time to scientific research,

"delivered alike from the temptations of wealth or the embarrassments of

poverty." That such a plan works well is amply attested by the results

emanating from the French academy. Pensionnaires in various branches of

science, however, either paid by the state or by learned societies, are

no longer confined to France.

Among the other early scientific societies was the Imperial Academy

of Sciences at St. Petersburg, projected by Peter the Great, and

established by his widow, Catharine I., in 1725; and also the Royal

Swedish Academy, incorporated in 1781, and counting among its early

members such men as the celebrated Linnaeus. But after the first impulse

had resulted in a few learned societies, their manifest advantage was

so evident that additional numbers increased rapidly, until at present

almost every branch of every science is represented by more or less

important bodies; and these are, individually and collectively, adding

to knowledge and stimulating interest in the many fields of science,

thus vindicating Lord Bacon's asseverations that knowledge could be

satisfactorily promulgated in this manner.

X. THE SUCCESSORS OF GALILEO IN PHYSICAL SCIENCE

We have now to witness the diversified efforts of a company of men who,

working for the most part independently, greatly added to the data of

the physical sciences--such men as Boyle, Huygens, Von Gericke, and

Hooke. It will be found that the studies of these men covered the whole

field of physical sciences as then understood--the field of so-called

natural philosophy. We shall best treat these successors of Galileo

and precursors of Newton somewhat biographically, pointing out the

correspondences and differences between their various accomplishments as

we proceed. It will be noted in due course that the work of some of them

was anticipatory of great achievements of a later century.

ROBERT BOYLE (1627-1691)

Some of Robert Boyle's views as to the possible structure of atmospheric

air will be considered a little farther on in this chapter, but for the

moment we will take up the consideration of some of his experiments

upon that as well as other gases. Boyle was always much interested

in alchemy, and carried on extensive experiments in attempting to

accomplish the transmutation of metals; but he did not confine himself

to these experiments, devoting himself to researches in all the fields

of natural philosophy. He was associated at Oxford with a company

of scientists, including Wallis and Wren, who held meetings and made

experiments together, these gatherings being the beginning, as mentioned

a moment ago, of what finally became the Royal Society. It was during

this residence at Oxford that many of his valuable researches upon air

were made, and during this time be invented his air-pump, now exhibited

in the Royal Society rooms at Burlington House.(1)

His experiments to prove the atmospheric pressure are most interesting

and conclusive. "Having three small, round glass bubbles, blown at the

flame of a lamp, about the size of hazel-nuts," he says, "each of them

with a short, slender stem, by means whereof they were so exactly poised

in water that a very small change of weight would make them either

emerge or sink; at a time when the atmosphere was of convenient weight,

I put them into a wide-mouthed glass of common water, and leaving them

in a quiet place, where they were frequently in my eye, I observed that

sometimes they would be at the top of the water, and remain there for

several days, or perhaps weeks, together, and sometimes fall to the

bottom, and after having continued there for some time rise again. And

sometimes they would rise or fall as the air was hot or cold."(2)

It was in the course of these experiments that the observations made by

Boyle led to the invention of his "statical barometer," the mercurial

barometer having been invented, as we have seen, by Torricelli, in 1643.

In describing this invention he says: "Making choice of a large, thin,

and light glass bubble, blown at the flame of a lamp, I counterpoised

it with a metallic weight, in a pair of scales that were suspended in

a frame, that would turn with the thirtieth part of a grain. Both the

frame and the balance were then placed near a good barometer, whence

I might learn the present weight of the atmosphere; when, though the

scales were unable to show all the variations that appeared in the

mercurial barometer, yet they gave notice of those that altered the

height of the mercury half a quarter of an inch."(3) A fairly sensitive

barometer, after all. This statical barometer suggested several useful

applications to the fertile imagination of its inventor, among others

the measuring of mountain-peaks, as with the mercurial barometer, the

rarefication of the air at the top giving a definite ratio to the more

condensed air in the valley.

Another of his experiments was made to discover the atmospheric pressure

to the square inch. After considerable difficulty he determined that the

relative weight of a cubic inch of water and mercury was about one to

fourteen, and computing from other known weights he determined that

"when a column of quicksilver thirty inches high is sustained in the

barometer, as it frequently happens, a column of air that presses upon

an inch square near the surface of the earth must weigh about fifteen

avoirdupois pounds."(4) As the pressure of air at the sea-level is now

estimated at 14.7304 pounds to the square inch, it will be seen that

Boyle's calculation was not far wrong.

From his numerous experiments upon the air, Boyle was led to believe

that there were many "latent qualities" due to substances contained in

it that science had as yet been unable to fathom, believing that there

is "not a more heterogeneous body in the world." He believed that

contagious diseases were carried by the air, and suggested that

eruptions of the earth, such as those made by earthquakes, might send

up "venomous exhalations" that produced diseases. He suggested also that

the air might play an important part in some processes of calcination,

which, as we shall see, was proved to be true by Lavoisier late in the

eighteenth century. Boyle's notions of the exact chemical action in

these phenomena were of course vague and indefinite, but he had observed

that some part was played by the air, and he was right in supposing that

the air "may have a great share in varying the salts obtainable from

calcined vitriol."(5)

Although he was himself such a painstaking observer of facts, he had

the fault of his age of placing too much faith in hear-say evidence of

untrained observers. Thus, from the numerous stories he heard concerning

the growth of metals in previously exhausted mines, he believed that the

air was responsible for producing this growth--in which he undoubtedly

believed. The story of a tin-miner that, in his own time, after a lapse

of only twenty-five years, a heap, of earth previously exhausted of

its ore became again even more richly impregnated than before by lying

exposed to the air, seems to have been believed by the philosopher.

As Boyle was an alchemist, and undoubtedly believed in the alchemic

theory that metals have "spirits" and various other qualities that do

not exist, it is not surprising that he was credulous in the matter of

beliefs concerning peculiar phenomena exhibited by them. Furthermore,

he undoubtedly fell into the error common to "specialists," or

persons working for long periods of time on one subject--the error of

over-enthusiasm in his subject. He had discovered so many remarkable

qualities in the air that it is not surprising to find that he

attributed to it many more that he could not demonstrate.

Boyle's work upon colors, although probably of less importance than his

experiments and deductions upon air, show that he was in the van as far

as the science of his day was concerned. As he points out, the schools

of his time generally taught that "color is a penetrating quality,

reaching to the innermost part of the substance," and, as an example

of this, sealing-wax was cited, which could be broken into minute bits,

each particle retaining the same color as its fellows or the original

mass. To refute this theory, and to show instances to the contrary,

Boyle, among other things, shows that various colors--blue, red,

yellow--may be produced upon tempered steel, and yet the metal within "a

hair's-breadth of its surface" have none of these colors. Therefore,

he was led to believe that color, in opaque bodies at least, is

superficial.

"But before we descend to a more particular consideration of our

subject," he says, "'tis proper to observe that colors may be

regarded either as a quality residing in bodies to modify light after a

particular manner, or else as light itself so modified as to strike upon

the organs of sight, and cause the sensation we call color; and that

this latter is the more proper acceptation of the word color will appear

hereafter. And indeed it is the light itself, which after a certain

manner, either mixed with shades or other-wise, strikes our eyes and

immediately produces that motion in the organ which gives us the color

of an object."(6)

In examining smooth and rough surfaces to determine the cause of their

color, he made use of the microscope, and pointed out the very obvious

example of the difference in color of a rough and a polished piece of

the same block of stone. He used some striking illustrations of the

effect of light and the position of the eye upon colors. "Thus the color

of plush or velvet will appear various if you stroke part of it one way

and part another, the posture of the particular threads in regard to the

light, or the eye, being thereby varied. And 'tis observable that in a

field of ripe corn, blown upon by the wind, there will appear waves of a

color different from that of the rest of the corn, because the wind, by

depressing some of the ears more than others, causes one to reflect more

light from the lateral and strawy parts than another."(7) His work upon

color, however, as upon light, was entirely overshadowed by the work of

his great fellow-countryman Newton.

Boyle's work on electricity was a continuation of Gilbert's, to which he

added several new facts. He added several substances to Gilbert's list

of "electrics," experimented on smooth and rough surfaces in exciting

of electricity, and made the important discovery that amber retained its

attractive virtue after the friction that excited it bad ceased. "For

the attrition having caused an intestine motion in its parts," he says,

"the heat thereby excited ought not to cease as soon as ever the rubbing

is over, but to continue capable of emitting effluvia for some time

afterwards, longer or shorter according to the goodness of the electric

and the degree of the commotion made; all which, joined together, may

sometimes make the effect considerable; and by this means, on a warm

day, I, with a certain body not bigger than a pea, but very vigorously

attractive, moved a steel needle, freely poised, about three minutes

after I had left off rubbing it."(8)

MARIOTTE AND VON GUERICKE

Working contemporaneously with Boyle, and a man whose name is usually

associated with his as the propounder of the law of density of

gases, was Edme Mariotte (died 1684), a native of Burgundy. Mariotte

demonstrated that but for the resistance of the atmosphere, all bodies,

whether light or heavy, dense or thin, would fall with equal rapidity,

and he proved this by the well-known "guinea-and-feather" experiment.

Having exhausted the air from a long glass tube in which a guinea piece

and a feather had been placed, he showed that in the vacuum thus formed

they fell with equal rapidity as often as the tube was reversed. From

his various experiments as to the pressure of the atmosphere he deduced

the law that the density and elasticity of the atmosphere are precisely

proportional to the compressing force (the law of Boyle and Mariotte).

He also ascertained that air existed in a state of mechanical

mixture with liquids, "existing between their particles in a state

of condensation." He made many other experiments, especially on

the collision of bodies, but his most important work was upon the

atmosphere.

But meanwhile another contemporary of Boyle and Mariotte was interesting

himself in the study of the atmosphere, and had made a wonderful

invention and a most striking demonstration. This was Otto von Guericke

(1602-1686), Burgomaster of Magdeburg, and councillor to his "most

serene and potent Highness" the elector of that place. When not

engrossed with the duties of public office, he devoted his time to the

study of the sciences, particularly pneumatics and electricity,

both then in their infancy. The discoveries of Galileo, Pascal, and

Torricelli incited him to solve the problem of the creation of a

vacuum--a desideratum since before the days of Aristotle. His first

experiments were with a wooden pump and a barrel of water, but he soon

found that with such porous material as wood a vacuum could not be

created or maintained. He therefore made use of a globe of copper, with

pump and stop-cock; and with this he was able to pump out air almost as

easily as water. Thus, in 1650, the air-pump was invented. Continuing

his experiments upon vacuums and atmospheric pressure with his newly

discovered pump, he made some startling discoveries as to the enormous

pressure exerted by the air.

It was not his intention, however, to demonstrate his newly acquired

knowledge by words or theories alone, nor by mere laboratory

experiments; but he chose instead an open field, to which were invited

Emperor Ferdinand III., and all the princes of the Diet at Ratisbon.

When they were assembled he produced two hollow brass hemispheres

about two feet in diameter, and placing their exactly fitting surfaces

together, proceeded to pump out the air from their hollow interior,

thus causing them to stick together firmly in a most remarkable way,

apparently without anything holding them. This of itself was strange

enough; but now the worthy burgomaster produced teams of horses, and

harnessing them to either side of the hemispheres, attempted to pull

the adhering brasses apart. Five, ten, fifteen teams--thirty horses,

in all--were attached; but pull and tug as they would they could not

separate the firmly clasped hemispheres. The enormous pressure of the

atmosphere had been most strikingly demonstrated.

But it is one thing to demonstrate, another to convince; and many of

the good people of Magdeburg shook their heads over this "devil's

contrivance," and predicted that Heaven would punish the Herr

Burgomaster, as indeed it had once by striking his house with lightning

and injuring some of his infernal contrivances. They predicted

his future punishment, but they did not molest him, for to his

fellow-citizens, who talked and laughed, drank and smoked with him, and

knew him for the honest citizen that he was, he did not seem bewitched

at all. And so he lived and worked and added other facts to science, and

his brass hemispheres were not destroyed by fanatical Inquisitors, but

are still preserved in the royal library at Berlin.

In his experiments with his air-pump he discovered many things regarding

the action of gases, among others, that animals cannot live in a vacuum.

He invented the anemoscope and the air-balance, and being thus enabled

to weight the air and note the changes that preceded storms and calms,

he was able still further to dumfound his wondering fellow-Magde-burgers

by more or less accurate predictions about the weather.

Von Guericke did not accept Gilbert's theory that the earth was a great

magnet, but in his experiments along lines similar to those pursued

by Gilbert, he not only invented the first electrical machine, but

discovered electrical attraction and repulsion. The electrical machine

which he invented consisted of a sphere of sulphur mounted on an iron

axis to imitate the rotation of the earth, and which, when rubbed,

manifested electrical reactions. When this globe was revolved and

stroked with the dry hand it was found that it attached to it "all sorts

of little fragments, like leaves of gold, silver, paper, etc." "Thus

this globe," he says, "when brought rather near drops of water causes

them to swell and puff up. It likewise attracts air, smoke, etc."(9)

Before the time of Guericke's demonstrations, Cabaeus had noted that

chaff leaped back from an "electric," but he did not interpret the

phenomenon as electrical repulsion. Von Guericke, however, recognized

it as such, and refers to it as what he calls "expulsive virtue." "Even

expulsive virtue is seen in this globe," he says, "for it not only

attracts, but also REPELS again from itself little bodies of this sort,

nor does it receive them until they have touched something else." It

will be observed from this that he was very close to discovering the

discharge of the electrification of attracted bodies by contact with

some other object, after which they are reattracted by the electric.

He performed a most interesting experiment with his sulphur globe and a

feather, and in doing so came near anticipating Benjamin Franklin in

his discovery of the effects of pointed conductors in drawing off the

discharge. Having revolved and stroked his globe until it repelled a bit

of down, he removed the globe from its rack and advancing it towards the

now repellent down, drove it before him about the room. In this chase

he observed that the down preferred to alight against "the points of any

object whatsoever." He noticed that should the down chance to be driven

within a few inches of a lighted candle, its attitude towards the globe

suddenly changed, and instead of running away from it, it now "flew to

it for protection"--the charge on the down having been dissipated by

the hot air. He also noted that if one face of a feather had been first

attracted and then repelled by the sulphur ball, that the surface so

affected was always turned towards the globe; so that if the positions

of the two were reversed, the sides of the feather reversed also.

Still another important discovery, that of electrical conduction,

was made by Von Guericke. Until his discovery no one had observed the

transference of electricity from one body to another, although Gilbert

had some time before noted that a rod rendered magnetic at one end

became so at the other. Von Guericke's experiments were made upon

a linen thread with his sulphur globe, which, he says, "having been

previously excited by rubbing, can exercise likewise its virtue through

a linen thread an ell or more long, and there attract something." But

this discovery, and his equally important one that the sulphur ball

becomes luminous when rubbed, were practically forgotten until again

brought to notice by the discoveries of Francis Hauksbee and Stephen

Gray early in the eighteenth century. From this we may gather that Von

Guericke himself did not realize the import of his discoveries, for

otherwise he would certainly have carried his investigations still

further. But as it was he turned his attention to other fields of

research.

ROBERT HOOKE

A slender, crooked, shrivelled-limbed, cantankerous little man, with

dishevelled hair and haggard countenance, bad-tempered and irritable,

penurious and dishonest, at least in his claims for priority in

discoveries--this is the picture usually drawn, alike by friends and

enemies, of Robert Hooke (1635-1703), a man with an almost unparalleled

genius for scientific discoveries in almost all branches of science.

History gives few examples so striking of a man whose really great

achievements in science would alone have made his name immortal, and yet

who had the pusillanimous spirit of a charlatan--an almost insane mania,

as it seems--for claiming the credit of discoveries made by others.

This attitude of mind can hardly be explained except as a mania: it is

certainly more charitable so to regard it. For his own discoveries and

inventions were so numerous that a few more or less would hardly

have added to his fame, as his reputation as a philosopher was well

established. Admiration for his ability and his philosophical knowledge

must always be marred by the recollection of his arrogant claims to the

discoveries of other philosophers.

It seems pretty definitely determined that Hooke should be credited with

the invention of the balance-spring for regulating watches; but for a

long time a heated controversy was waged between Hooke and Huygens as to

who was the real inventor. It appears that Hooke conceived the idea

of the balance-spring, while to Huygens belongs the credit of having

adapted the COILED spring in a working model. He thus made practical

Hooke's conception, which is without value except as applied by

the coiled spring; but, nevertheless, the inventor, as well as the

perfector, should receive credit. In this controversy, unlike many

others, the blame cannot be laid at Hooke's door.

Hooke was the first curator of the Royal Society, and when anything was

to be investigated, usually invented the mechanical devices for doing

so. Astronomical apparatus, instruments for measuring specific weights,

clocks and chronometers, methods of measuring the velocity of falling

bodies, freezing and boiling points, strength of gunpowder, magnetic

instruments--in short, all kinds of ingenious mechanical devices in

all branches of science and mechanics. It was he who made the famous

air-pump of Robert Boyle, based on Boyle's plans. Incidentally, Hooke

claimed to be the inventor of the first air-pump himself, although this

claim is now entirely discredited.

Within a period of two years he devised no less than thirty different

methods of flying, all of which, of course, came to nothing, but go to

show the fertile imagination of the man, and his tireless energy. He

experimented with electricity and made some novel suggestions upon the

difference between the electric spark and the glow, although on the

whole his contributions in this field are unimportant. He also first

pointed out that the motions of the heavenly bodies must be looked upon

as a mechanical problem, and was almost within grasping distance of the

exact theory of gravitation, himself originating the idea of making use

of the pendulum in measuring gravity. Likewise, he first proposed the

wave theory of light; although it was Huygens who established it on its

present foundation.

Hooke published, among other things, a book of plates and descriptions

of his Microscopical Observations, which gives an idea of the advance

that had already been made in microscopy in his time. Two of these

plates are given here, which, even in this age of microscopy, are

both interesting and instructive. These plates are made from prints of

Hooke's original copper plates, and show that excellent lenses were

made even at that time. They illustrate, also, how much might have been

accomplished in the field of medicine if more attention had been given

to microscopy by physicians. Even a century later, had physicians made

better use of their microscopes, they could hardly have overlooked such

an easily found parasite as the itch mite, which is quite as easily

detected as the cheese mite, pictured in Hooke's book.

In justice to Hooke, and in extenuation of his otherwise inexcusable

peculiarities of mind, it should be remembered that for many years he

suffered from a painful and wasting disease. This may have affected his

mental equilibrium, without appreciably affecting his ingenuity. In his

own time this condition would hardly have been considered a disease; but

to-day, with our advanced ideas as to mental diseases, we should be more

inclined to ascribe his unfortunate attitude of mind to a pathological

condition, rather than to any manifestation of normal mentality.

From this point of view his mental deformity seems not unlike that of

Cavendish's, later, except that in the case of Cavendish it manifested

itself as an abnormal sensitiveness instead of an abnormal irritability.

CHRISTIAN HUYGENS

If for nothing else, the world is indebted to the man who invented the

pendulum clock, Christian Huygens (1629-1695), of the Hague, inventor,

mathematician, mechanician, astronomer, and physicist. Huygens was

the descendant of a noble and distinguished family, his father, Sir

Constantine Huygens, being a well-known poet and diplomatist. Early in

life young Huygens began his career in the legal profession, completing

his education in the juridical school at Breda; but his taste for

mathematics soon led him to neglect his legal studies, and his aptitude

for scientific researches was so marked that Descartes predicted great

things of him even while he was a mere tyro in the field of scientific

investigation.

One of his first endeavors in science was to attempt an improvement

of the telescope. Reflecting upon the process of making lenses then in

vogue, young Huygens and his brother Constantine attempted a new method

of grinding and polishing, whereby they overcame a great deal of the

spherical and chromatic aberration. With this new telescope a much

clearer field of vision was obtained, so much so that Huygens was able

to detect, among other things, a hitherto unknown satellite of Saturn.

It was these astronomical researches that led him to apply the pendulum

to regulate the movements of clocks. The need for some more exact method

of measuring time in his observations of the stars was keenly felt by

the young astronomer, and after several experiments along different

lines, Huygens hit upon the use of a swinging weight; and in 1656 made

his invention of the pendulum clock. The year following, his clock

was presented to the states-general. Accuracy as to time is absolutely

essential in astronomy, but until the invention of Huygens's clock there

was no precise, nor even approximately precise, means of measuring short

intervals.

Huygens was one of the first to adapt the micrometer to the telescope--a

mechanical device on which all the nice determination of minute

distances depends. He also took up the controversy against Hooke as

to the superiority of telescopic over plain sights to quadrants, Hooke

contending in favor of the plain. In this controversy, the subject of

which attracted wide attention, Huygens was completely victorious;

and Hooke, being unable to refute Huygens's arguments, exhibited such

irritability that he increased his already general unpopularity. All of

the arguments for and against the telescope sight are too numerous to

be given here. In contending in its favor Huygens pointed out that the

unaided eye is unable to appreciate an angular space in the sky less

than about thirty seconds. Even in the best quadrant with a plain sight,

therefore, the altitude must be uncertain by that quantity. If in place

of the plain sight a telescope is substituted, even if it magnify only

thirty times, it will enable the observer to fix the position to one

second, with progressively increased accuracy as the magnifying power

of the telescope is increased. This was only one of the many telling

arguments advanced by Huygens.

In the field of optics, also, Huygens has added considerably to science,

and his work, Dioptrics, is said to have been a favorite book with

Newton. During the later part of his life, however, Huygens again

devoted himself to inventing and constructing telescopes, grinding the

lenses, and devising, if not actually making, the frame for holding

them. These telescopes were of enormous lengths, three of his

object-glasses, now in possession of the Royal Society, being of 123,

180, and 210 feet focal length respectively. Such instruments,

if constructed in the ordinary form of the long tube, were very

unmanageable, and to obviate this Huygens adopted the plan of dispensing

with the tube altogether, mounting his lenses on long poles manipulated

by machinery. Even these were unwieldy enough, but the difficulties of

manipulation were fully compensated by the results obtained.

It had been discovered, among other things, that in oblique refraction

light is separated into colors. Therefore, any small portion of the

convex lens of the telescope, being a prism, the rays proceed to the

focus, separated into prismatic colors, which make the image thus formed

edged with a fringe of color and indistinct. But, fortunately for the

early telescope makers, the degree of this aberration is independent of

the focal length of the lens; so that, by increasing this focal length

and using the appropriate eye-piece, the image can be greatly magnified,

while the fringe of colors remains about the same as when a less

powerful lens is used. Hence the advantage of Huygens's long telescope.

He did not confine his efforts to simply lengthening the focal length of

his telescopes, however, but also added to their efficiency by inventing

an almost perfect achromatic eye-piece.

In 1663 he was elected a fellow of the Royal Society of London, and in

1669 he gave to that body a concise statement of the laws governing the

collision of elastic bodies. Although the same views had been given by

Wallis and Wren a few weeks earlier, there is no doubt that Huygens's

views were reached independently; and it is probable that he had

arrived at his conclusions several years before. In the Philosophical

Transactions for 1669 it is recorded that the society, being interested

in the laws of the principles of motion, a request was made that M.

Huygens, Dr. Wallis, and Sir Christopher Wren submit their views on the

subject. Wallis submitted his paper first, November 15, 1668. A month

later, December 17th, Wren imparted to the society his laws as to the

nature of the collision of bodies. And a few days later, January 5,

1669, Huygens sent in his "Rules Concerning the Motion of Bodies after

Mutual Impulse." Although Huygens's report was received last, he was

anticipated by such a brief space of time, and his views are so clearly

stated--on the whole rather more so than those of the other two--that we

give them in part here:

"1. If a hard body should strike against a body equally hard at rest,

after contact the former will rest and the latter acquire a velocity

equal to that of the moving body.

"2. But if that other equal body be likewise in motion, and moving

in the same direction, after contact they will move with reciprocal

velocities.

"3. A body, however great, is moved by a body however small impelled

with any velocity whatsoever.

"5. The quantity of motion of two bodies may be either increased or

diminished by their shock; but the same quantity towards the same part

remains, after subtracting the quantity of the contrary motion.

"6. The sum of the products arising from multiplying the mass of any

hard body into the squares of its velocity is the same both before and

after the stroke.

"7. A hard body at rest will receive a greater quantity of motion

from another hard body, either greater or less than itself, by the

interposition of any third body of a mean quantity, than if it was

immediately struck by the body itself; and if the interposing body be a

mean proportional between the other two, its action upon the quiescent

body will be the greatest of all."(10)

This was only one of several interesting and important communications

sent to the Royal Society during his lifetime. One of these was a report

on what he calls "Pneumatical Experiments." "Upon including in a vacuum

an insect resembling a beetle, but somewhat larger," he says, "when it

seemed to be dead, the air was readmitted, and soon after it revived;

putting it again in the vacuum, and leaving it for an hour, after which

the air was readmitted, it was observed that the insect required a

longer time to recover; including it the third time for two days, after

which the air was admitted, it was ten hours before it began to stir;

but, putting it in a fourth time, for eight days, it never afterwards

recovered.... Several birds, rats, mice, rabbits, and cats were killed

in a vacuum, but if the air was admitted before the engine was quite

exhausted some of them would recover; yet none revived that had been

in a perfect vacuum.... Upon putting the weight of eighteen grains of

powder with a gauge into a receiver that held several pounds of water,

and firing the powder, it raised the mercury an inch and a half; from

which it appears that there is one-fifth of air in gunpowder, upon the

supposition that air is about one thousand times lighter than water; for

in this experiment the mercury rose to the eighteenth part of the height

at which the air commonly sustains it, and consequently the weight of

eighteen grains of powder yielded air enough to fill the eighteenth part

of a receiver that contained seven pounds of water; now this eighteenth

part contains forty-nine drachms of water; wherefore the air, that takes

up an equal space, being a thousand times lighter, weighs one-thousandth

part of forty-nine drachms, which is more than three grains and a half;

it follows, therefore, that the weight of eighteen grains of powder

contains more than three and a half of air, which is about one-fifth of

eighteen grains...."

From 1665 to 1681, accepting the tempting offer made him through

Colbert, by Louis XIV., Huygens pursued his studies at the Bibliotheque

du Roi as a resident of France. Here he published his Horologium

Oscillatorium, dedicated to the king, containing, among other things,

his solution of the problem of the "centre of oscillation." This in

itself was an important step in the history of mechanics. Assuming as

true that the centre of gravity of any number of interdependent bodies

cannot rise higher than the point from which it falls, he reached

correct conclusions as to the general principle of the conservation of

vis viva, although he did not actually prove his conclusions. This was

the first attempt to deal with the dynamics of a system. In this work,

also, was the true determination of the relation between the length of a

pendulum and the time of its oscillation.

In 1681 he returned to Holland, influenced, it is believed, by the

attitude that was being taken in France against his religion. Here he

continued his investigations, built his immense telescopes, and, among

other things, discovered "polarization," which is recorded in Traite

de la Lumiere, published at Leyden in 1690. Five years later he

died, bequeathing his manuscripts to the University of Leyden. It

is interesting to note that he never accepted Newton's theory of

gravitation as a universal property of matter.

XI. NEWTON AND THE COMPOSITION OF LIGHT

Galileo, that giant in physical science of the early seventeenth

century, died in 1642. On Christmas day of the same year there was born

in England another intellectual giant who was destined to carry forward

the work of Copernicus, Kepler, and Galileo to a marvellous consummation

through the discovery of the great unifying law in accordance with

which the planetary motions are performed. We refer, of course, to the

greatest of English physical scientists, Isaac Newton, the Shakespeare

of the scientific world. Born thus before the middle of the seventeenth

century, Newton lived beyond the first quarter of the eighteenth

(1727). For the last forty years of that period his was the dominating

scientific personality of the world. With full propriety that time has

been spoken of as the "Age of Newton."

Yet the man who was to achieve such distinction gave no early

premonition of future greatness. He was a sickly child from birth, and

a boy of little seeming promise. He was an indifferent student, yet, on

the other hand, he cared little for the common amusements of boyhood. He

early exhibited, however, a taste for mechanical contrivances, and spent

much time in devising windmills, water-clocks, sun-dials, and kites.

While other boys were interested only in having kites that would

fly, Newton--at least so the stories of a later time would have us

understand--cared more for the investigation of the seeming principles

involved, or for testing the best methods of attaching the strings, or

the best materials to be used in construction.

Meanwhile the future philosopher was acquiring a taste for reading and

study, delving into old volumes whenever he found an opportunity. These

habits convinced his relatives that it was useless to attempt to make a

farmer of the youth, as had been their intention. He was therefore sent

back to school, and in the summer of 1661 he matriculated at Trinity

College, Cambridge. Even at college Newton seems to have shown no

unusual mental capacity, and in 1664, when examined for a scholarship by

Dr. Barrow, that gentleman is said to have formed a poor opinion of the

applicant. It is said that the knowledge of the estimate placed upon

his abilities by his instructor piqued Newton, and led him to take up

in earnest the mathematical studies in which he afterwards attained such

distinction. The study of Euclid and Descartes's "Geometry" roused in

him a latent interest in mathematics, and from that time forward his

investigations were carried on with enthusiasm. In 1667 he was elected

Fellow of Trinity College, taking the degree of M.A. the following

spring.

It will thus appear that Newton's boyhood and early manhood were passed

during that troublous time in British political annals which saw the

overthrow of Charles I., the autocracy of Cromwell, and the eventual

restoration of the Stuarts. His maturer years witnessed the overthrow of

the last Stuart and the reign of the Dutchman, William of Orange. In his

old age he saw the first of the Hanoverians mount the throne of England.

Within a decade of his death such scientific path-finders as Cavendish,

Black, and Priestley were born--men who lived on to the close of the

eighteenth century. In a full sense, then, the age of Newton bridges

the gap from that early time of scientific awakening under Kepler

and Galileo to the time which we of the twentieth century think of as

essentially modern.

THE COMPOSITION OF WHITE LIGHT

In December, 1672, Newton was elected a Fellow of the Royal Society,

and at this meeting a paper describing his invention of the refracting

telescope was read. A few days later he wrote to the secretary, making

some inquiries as to the weekly meetings of the society, and intimating

that he had an account of an interesting discovery that he wished to lay

before the society. When this communication was made public, it proved

to be an explanation of the discovery of the composition of white light.

We have seen that the question as to the nature of color had commanded

the attention of such investigators as Huygens, but that no very

satisfactory solution of the question had been attained. Newton proved

by demonstrative experiments that white light is composed of the

blending of the rays of diverse colors, and that the color that we

ascribe to any object is merely due to the fact that the object in

question reflects rays of that color, absorbing the rest. That white

light is really made up of many colors blended would seem incredible

had not the experiments by which this composition is demonstrated become

familiar to every one. The experiments were absolutely novel when Newton

brought them forward, and his demonstration of the composition of light

was one of the most striking expositions ever brought to the

attention of the Royal Society. It is hardly necessary to add that,

notwithstanding the conclusive character of Newton's work, his

explanations did not for a long time meet with general acceptance.

Newton was led to his discovery by some experiments made with an

ordinary glass prism applied to a hole in the shutter of a darkened

room, the refracted rays of the sunlight being received upon the

opposite wall and forming there the familiar spectrum. "It was a very

pleasing diversion," he wrote, "to view the vivid and intense colors

produced thereby; and after a time, applying myself to consider them

very circumspectly, I became surprised to see them in varying form,

which, according to the received laws of refraction, I expected should

have been circular. They were terminated at the sides with straight

lines, but at the ends the decay of light was so gradual that it was

difficult to determine justly what was their figure, yet they seemed

semicircular.

"Comparing the length of this colored spectrum with its breadth, I found

it almost five times greater; a disproportion so extravagant that it

excited me to a more than ordinary curiosity of examining from whence it

might proceed. I could scarce think that the various thicknesses of

the glass, or the termination with shadow or darkness, could have any

influence on light to produce such an effect; yet I thought it not

amiss, first, to examine those circumstances, and so tried what would

happen by transmitting light through parts of the glass of divers

thickness, or through holes in the window of divers bigness, or by

setting the prism without so that the light might pass through it and be

refracted before it was transmitted through the hole; but I found none

of those circumstances material. The fashion of the colors was in all

these cases the same.

"Then I suspected whether by any unevenness of the glass or other

contingent irregularity these colors might be thus dilated. And to try

this I took another prism like the former, and so placed it that the

light, passing through them both, might be refracted contrary ways,

and so by the latter returned into that course from which the former

diverted it. For, by this means, I thought, the regular effects of the

first prism would be destroyed by the second prism, but the irregular

ones more augmented by the multiplicity of refractions. The event was

that the light, which by the first prism was diffused into an oblong

form, was by the second reduced into an orbicular one with as much

regularity as when it did not all pass through them. So that, whatever

was the cause of that length, 'twas not any contingent irregularity.

"I then proceeded to examine more critically what might be effected by

the difference of the incidence of rays coming from divers parts of the

sun; and to that end measured the several lines and angles belonging to

the image. Its distance from the hole or prism was 22 feet; its utmost

length 13 1/4 inches; its breadth 2 5/8; the diameter of the hole 1/4

of an inch; the angle which the rays, tending towards the middle of the

image, made with those lines, in which they would have proceeded without

refraction, was 44 degrees 56'; and the vertical angle of the prism, 63

degrees 12'. Also the refractions on both sides of the prism--that is,

of the incident and emergent rays--were, as near as I could make

them, equal, and consequently about 54 degrees 4'; and the rays fell

perpendicularly upon the wall. Now, subducting the diameter of the hole

from the length and breadth of the image, there remains 13 inches

the length, and 2 3/8 the breadth, comprehended by those rays, which,

passing through the centre of the said hole, which that breadth

subtended, was about 31', answerable to the sun's diameter; but the

angle which its length subtended was more than five such diameters,

namely 2 degrees 49'.

"Having made these observations, I first computed from them the

refractive power of the glass, and found it measured by the ratio of the

sines 20 to 31. And then, by that ratio, I computed the refractions

of two rays flowing from opposite parts of the sun's discus, so as to

differ 31' in their obliquity of incidence, and found that the emergent

rays should have comprehended an angle of 31', as they did, before they

were incident.

"But because this computation was founded on the hypothesis of the

proportionality of the sines of incidence and refraction, which though

by my own experience I could not imagine to be so erroneous as to make

that angle but 31', which in reality was 2 degrees 49', yet my curiosity

caused me again to make my prism. And having placed it at my window,

as before, I observed that by turning it a little about its axis to and

fro, so as to vary its obliquity to the light more than an angle of 4

degrees or 5 degrees, the colors were not thereby sensibly translated

from their place on the wall, and consequently by that variation of

incidence the quantity of refraction was not sensibly varied. By this

experiment, therefore, as well as by the former computation, it was

evident that the difference of the incidence of rays flowing from divers

parts of the sun could not make them after decussation diverge at a

sensibly greater angle than that at which they before converged; which

being, at most, but about 31' or 32', there still remained some other

cause to be found out, from whence it could be 2 degrees 49'."

All this caused Newton to suspect that the rays, after their trajection

through the prism, moved in curved rather than in straight lines, thus

tending to be cast upon the wall at different places according to the

amount of this curve. His suspicions were increased, also, by happening

to recall that a tennis-ball sometimes describes such a curve when "cut"

by a tennis-racket striking the ball obliquely.

"For a circular as well as a progressive motion being communicated to

it by the stroke," he says, "its parts on that side where the motions

conspire must press and beat the contiguous air more violently than

on the other, and there excite a reluctancy and reaction of the air

proportionately greater. And for the same reason, if the rays of light

should possibly be globular bodies, and by their oblique passage out of

one medium into another acquire a circulating motion, they ought to feel

the greater resistance from the ambient ether on that side where the

motions conspire, and thence be continually bowed to the other. But

notwithstanding this plausible ground of suspicion, when I came to

examine it I could observe no such curvity in them. And, besides (which

was enough for my purpose), I observed that the difference 'twixt the

length of the image and diameter of the hole through which the light was

transmitted was proportionable to their distance.

"The gradual removal of these suspicions at length led me to the

experimentum crucis, which was this: I took two boards, and, placing

one of them close behind the prism at the window, so that the light must

pass through a small hole, made in it for the purpose, and fall on the

other board, which I placed at about twelve feet distance, having first

made a small hole in it also, for some of the incident light to pass

through. Then I placed another prism behind this second board, so that

the light trajected through both the boards might pass through that

also, and be again refracted before it arrived at the wall. This done,

I took the first prism in my hands and turned it to and fro slowly about

its axis, so much as to make the several parts of the image, cast on

the second board, successively pass through the hole in it, that I might

observe to what places on the wall the second prism would refract them.

And I saw by the variation of these places that the light, tending to

that end of the image towards which the refraction of the first prism

was made, did in the second prism suffer a refraction considerably

greater than the light tending to the other end. And so the true cause

of the length of that image was detected to be no other than that LIGHT

consists of RAYS DIFFERENTLY REFRANGIBLE, which, without any respect

to a difference in their incidence, were, according to their degrees of

refrangibility, transmitted towards divers parts of the wall."(1)

THE NATURE OF COLOR

Having thus proved the composition of light, Newton took up an

exhaustive discussion as to colors, which cannot be entered into at

length here. Some of his remarks on the subject of compound colors,

however, may be stated in part. Newton's views are of particular

interest in this connection, since, as we have already pointed out, the

question as to what constituted color could not be agreed upon by

the philosophers. Some held that color was an integral part of the

substance; others maintained that it was simply a reflection from the

surface; and no scientific explanation had been generally accepted.

Newton concludes his paper as follows:

"I might add more instances of this nature, but I shall conclude with

the general one that the colors of all natural bodies have no other

origin than this, that they are variously qualified to reflect one sort

of light in greater plenty than another. And this I have experimented

in a dark room by illuminating those bodies with uncompounded light of

divers colors. For by that means any body may be made to appear of any

color. They have there no appropriate color, but ever appear of the

color of the light cast upon them, but yet with this difference, that

they are most brisk and vivid in the light of their own daylight color.

Minium appeareth there of any color indifferently with which 'tis

illustrated, but yet most luminous in red; and so Bise appeareth

indifferently of any color with which 'tis illustrated, but yet most

luminous in blue. And therefore Minium reflecteth rays of any color, but

most copiously those indued with red; and consequently, when

illustrated with daylight--that is, with all sorts of rays promiscuously

blended--those qualified with red shall abound most in the reflected

light, and by their prevalence cause it to appear of that color. And for

the same reason, Bise, reflecting blue most copiously, shall appear

blue by the excess of those rays in its reflected light; and the like

of other bodies. And that this is the entire and adequate cause of their

colors is manifest, because they have no power to change or alter

the colors of any sort of rays incident apart, but put on all colors

indifferently with which they are enlightened."(2)