A History of Science, vol 4 - Henry Smith Williams (epub e ink reader .txt) 📗

contributed to the same end, from a source that could

hardly have been imagined when the Proutian hypothesis, was

formulated, through the tradition of a novel weapon to the

armamentarium of the chemist—the spectroscope. The perfection

of this instrument, in the hands of two German scientists, Gustav

Robert Kirchhoff and Robert Wilhelm Bunsen, came about through

the investigation, towards the middle of the century, of the

meaning of the dark lines which had been observed in the solar

spectrum by Fraunhofer as early as 1815, and by Wollaston a

decade earlier. It was suspected by Stokes and by Fox Talbot in

England, but first brought to demonstration by Kirchhoff and

Bunsen, that these lines, which were known to occupy definite

positions in the spectrum, are really indicative of particular

elementary substances. By means of the spectroscope, which is

essentially a magnifying lens attached to a prism of glass, it is

possible to locate the lines with great accuracy, and it was soon

shown that here was a new means of chemical analysis of the most

exquisite delicacy. It was found, for example, that the

spectroscope could detect the presence of a quantity of sodium so

infinitesimal as the one two-hundred-thousandth of a grain. But

what was even more important, the spectroscope put no limit upon

the distance of location of the substance it tested, provided

only that sufficient light came from it. The experiments it

recorded might be performed in the sun, or in the most distant

stars or nebulae; indeed, one of the earliest feats of the

instrument was to wrench from the sun the secret of his chemical

constitution.

 

To render the utility of the spectroscope complete, however, it

was necessary to link with it another new chemical

agency—namely, photography. This now familiar process is based

on the property of light to decompose certain unstable compounds

of silver, and thus alter their chemical composition. Davy and

Wedgwood barely escaped the discovery of the value of the

photographic method early in the nineteenth century. Their

successors quite overlooked it until about 1826, when Louis J. M.

Daguerre, the French chemist, took the matter in hand, and after

many years of experimentation brought it to relative perfection

in 1839, in which year the famous daguerreotype first brought the

matter to popular attention. In the same year Mr. Fox Talbot read

a paper on the subject before the Royal Society, and soon

afterwards the efforts of Herschel and numerous other natural

philosophers contributed to the advancement of the new method.

 

In 1843 Dr. John W. Draper, the famous English-American chemist

and physiologist, showed that by photography the Fraunhofer lines

in the solar spectrum might be mapped with absolute accuracy;

also proving that the silvered film revealed many lines invisible

to the unaided eye. The value of this method of observation was

recognized at once, and, as soon as the spectroscope was

perfected, the photographic method, in conjunction with its use,

became invaluable to the chemist. By this means comparisons of

spectra may be made with a degree of accuracy not otherwise

obtainable; and, in case of the stars, whole clusters of spectra

may be placed on record at a single observation.

 

As the examination of the sun and stars proceeded, chemists were

amazed or delighted, according to their various preconceptions,

to witness the proof that many familiar terrestrial elements are

to be found in the celestial bodies. But what perhaps surprised

them most was to observe the enormous preponderance in the

sidereal bodies of the element hydrogen. Not only are there vast

quantities of this element in the sun’s atmosphere, but some

other suns appeared to show hydrogen lines almost exclusively in

their spectra. Presently it appeared that the stars of which

this is true are those white stars, such as Sirius, which had

been conjectured to be the hottest; whereas stars that are only

red-hot, like our sun, show also the vapors of many other

elements, including iron and other metals.

 

In 1878 Professor J. Norman Lockyer, in a paper before the Royal

Society, called attention to the possible significance of this

series of observations. He urged that the fact of the sun showing

fewer elements than are observed here on the cool earth, while

stars much hotter than the sun show chiefly one element, and that

one hydrogen, the lightest of known elements, seemed to give

color to the possibility that our alleged elements are really

compounds, which at the temperature of the hottest stars may be

decomposed into hydrogen, the latter “element” itself being also

doubtless a compound, which might be resolved under yet more

trying conditions.

 

Here, then, was what might be termed direct experimental evidence

for the hypothesis of Prout. Unfortunately, however, it is

evidence of a kind which only a few experts are competent to

discuss—so very delicate a matter is the spectral analysis of

the stars. What is still more unfortunate, the experts do not

agree among themselves as to the validity of Professor Lockyer’s

conclusions. Some, like Professor Crookes, have accepted them

with acclaim, hailing Lockyer as “the Darwin of the inorganic

world,” while others have sought a different explanation of the

facts he brings forward. As yet it cannot be said that the

controversy has been brought to final settlement. Still, it is

hardly to be doubted that now, since the periodic law has seemed

to join hands with the spectroscope, a belief in the compound

nature of the so-called elements is rapidly gaining ground among

chemists. More and more general becomes the belief that the

Daltonian atom is really a compound radical, and that back of the

seeming diversity of the alleged elements is a single form of

primordial matter. Indeed, in very recent months, direct

experimental evidence for this view has at last come to hand,

through the study of radio-active substances. In a later chapter

we shall have occasion to inquire how this came about.

 

IV. ANATOMY AND PHYSIOLOGY IN THE EIGHTEENTH CENTURY

ALBRECHT VON HALLER

An epoch in physiology was made in the eighteenth century by the

genius and efforts of Albrecht von Haller (1708-1777), of Berne,

who is perhaps as worthy of the title “The Great” as any

philosopher who has been so christened by his contemporaries

since the time of Hippocrates. Celebrated as a physician, he was

proficient in various fields, being equally famed in his own time

as poet, botanist, and statesman, and dividing his attention

between art and science.

 

As a child Haller was so sickly that he was unable to amuse

himself with the sports and games common to boys of his age, and

so passed most of his time poring over books. When ten years of

age he began writing poems in Latin and German, and at fifteen

entered the University of Tubingen. At seventeen he wrote

learned articles in opposition to certain accepted doctrines, and

at nineteen he received his degree of doctor. Soon after this he

visited England, where his zeal in dissecting brought him under

suspicion of grave-robbery, which suspicion made it expedient for

him to return to the Continent. After studying botany in Basel

for some time he made an extended botanical journey through

Switzerland, finally settling in his native city, Berne, as a

practising physician. During this time he did not neglect either

poetry or botany, publishing anonymously a collection of poems.

 

In 1736 he was called to Gottingen as professor of anatomy,

surgery, chemistry, and botany. During his labors in the

university he never neglected his literary work, sometimes living

and sleeping for days and nights together in his library, eating

his meals while delving in his books, and sleeping only when

actually compelled to do so by fatigue. During all this time he

was in correspondence with savants from all over the world, and

it is said of him that he never left a letter of any kind

unanswered.

 

Haller’s greatest contribution to medical science was his famous

doctrine of irritability, which has given him the name of “father

of modern nervous physiology,” just as Harvey is called “the

father of the modern physiology of the blood.” It has been said

of this famous doctrine of irritability that “it moved all the

minds of the century—and not in the departments of medicine

alone—in a way of which we of the present day have no

satisfactory conception, unless we compare it with our modern

Darwinism.”[1]

 

The principle of general irritability had been laid down by

Francis Glisson (1597-1677) from deductive studies, but Haller

proved by experiments along the line of inductive methods that

this irritability was not common to all “fibre as well as to the

fluids of the body,” but something entirely special, and peculiar

only to muscular substance. He distinguished between irritability

of muscles and sensibility of nerves. In 1747 he gave as the

three forces that produce muscular movements: elasticity, or

“dead nervous force”; irritability, or “innate nervous force”;

and nervous force in itself. And in 1752 he described one

hundred and ninety experiments for determining what parts of the

body possess “irritability”—that is, the property of contracting

when stimulated. His conclusion that this irritability exists in

muscular substance alone and is quite independent of the nerves

proceeding to it aroused a controversy that was never definitely

settled until late in the nineteenth century, when Haller’s

theory was found to be entirely correct.

 

It was in pursuit of experiments to establish his theory of

irritability that Haller made his chief discoveries in embryology

and development. He proved that in the process of incubation of

the egg the first trace of the heart of the chick shows itself in

the thirty-eighth hour, and that the first trace of red blood

showed in the forty-first hour. By his investigations upon the

lower animals he attempted to confirm the theory that since the

creation of genus every individual is derived from a preceding

individual—the existing theory of preformation, in which he

believed, and which taught that “every individual is fully and

completely preformed in the germ, simply growing from microscopic

to visible proportions, without developing any new parts.”

 

In physiology, besides his studies of the nervous system, Haller

studied the mechanism of respiration, refuting the teachings of

Hamberger (1697-1755), who maintained that the lungs contract

independently. Haller, however, in common with his

contemporaries, failed utterly to understand the true function of

the lungs. The great physiologist’s influence upon practical

medicine, while most profound, was largely indirect. He was a

theoretical rather than a practical physician, yet he is credited

with being the first physician to use the watch in counting the

pulse.

BATTISTA MORGAGNI AND MORBID ANATOMY

A great contemporary of Haller was Giovanni Battista Morgagni

(1682-1771), who pursued what Sydenham had neglected, the

investigation in anatomy, thus supplying a necessary counterpart

to the great Englishman’s work. Morgagni’s investigations were

directed chiefly to the study of morbid anatomy—the study of the

structure of diseased tissue, both during life and post mortem,

in contrast to the normal anatomical structures. This work cannot

be said to have originated with him; for as early as 1679 Bonnet

had made similar, although less extensive, studies; and later

many investigators, such as Lancisi and Haller, had made

post-mortem studies. But Morgagni’s De sedibus et causis

morborum per anatomen indagatis was the largest, most accurate,

and best-illustrated collection of cases that had ever been

brought together, and marks an epoch in medical science. From the

time of the publication of Morgagni’s researches, morbid anatomy

became a recognized branch of the medical science, and the effect

of the impetus thus given it has been steadily increasing since

that time.

WILLIAM HUNTER

William Hunter (1718-1783) must always be remembered as one of

the greatest physicians and anatomists of the eighteenth century,

and particularly as the first great teacher of anatomy in

England; but his fame has been somewhat overshadowed by that of

his younger brother John.

 

Hunter had