Charles Darwin and the Development of Science.
[=Progress of Scientific Discovery in the Past=]
Science by no means belongs to the nineteenth century. It has been
extant upon the earth ever since man began to observe and consider the
marvels of the universe. We can trace it back to an age possibly ten
thousand years remote, when men began to watch and record the movements
of the stars in the heavens above the broad Babylonian plain. It grew
active among the Greeks of Alexandria in that too brief period before
the hand of war checked for centuries the progress of mankind. It rose
again in Europe during the mediæval period, and became active during
the later centuries of this period. In the centuries immediately
preceding the nineteenth numbers of great scientists arose, and many
highly important discoveries were made, while theoretical science
achieved a remarkable progress, its ranks being adorned by such names
as those of Copernicus, Kepler, Galileo, Newton, and various others of
world-wide fame that might be given. Thus at the dawn of the nineteenth
century there existed a great groundwork of scientific facts and
theories upon which to build the massive future edifice.
[=Scientific Activity of the Nineteenth Century=]
This building has been going on with extraordinary rapidity during the
present century, and to-day our knowledge of the facts of science is
immensely greater than that of our predecessors of a century ago; while
of the views entertained and theories promulgated previous to 1800, the
great sum have been thrown overboard and replaced by others founded
upon a much wider and deeper knowledge of facts.
New and important theoretical views of science have been reached in
all departments. Recent chemistry, for instance, is a very different
thing from the chemistry of a century ago. Geology has been largely
transformed within the century. Heat, once supposed to be a substance,
is now known to be a motion; light, formerly thought to be a direct
motion of particles, is now believed to be a wave motion; new and
important conceptions have been reached concerning electricity and
magnetism; and our knowledge of the various sciences that have to
do with the world of life is extraordinarily advanced. As for the
practical applications of science, it may suffice to present the
startling fact that the substance of the atmosphere, scarcely known
a century ago, can now be reduced to a liquid and carried about like
water in a bucket.
In view of the facts here briefly stated it might almost be said that
science, as it exists to-day, is a result of nineteenth century thought
and observation; since that of the past was largely theoretical and
the bulk of its theories have been set aside, while the scientific
observations of former times were but a drop in the bucket as compared
with the vast multitude of those of the past hundred years. As regards
the utilization of scientific facts, their application to the benefit
of mankind, this is almost solely the work of the century under review,
and in no direction has invention produced more wonderful and useful
results.
[=Wallace's "Wonderful Century"=]
[=Epoch-Making Discoveries of Past Times=]
Alfred Russell Wallace, one of the most distinguished scientists of
recent times, in his work entitled "The Wonderful Century," has made
a careful inventory of the discoveries and inventions to which the
progress of mankind is mainly due, and he divides them into two groups,
the first embracing all the epoch-making discoveries achieved by men
previous to the present century, and the second taking in the steps of
progress of equal importance which have been made in the nineteenth
century. In the first list he finds only fifteen items of the highest
rank, and the claims of some even of these to a separate place are
not beyond question, since they may not really be of epoch-making
character. He puts first in the list the following, viz.: Alphabetic
writing and the Arabic notation, which have always been powerful
engines of knowledge and discovery. Their inventors are unknown, lost
in the dim twilight of prehistoric times. As the third great discovery
of ancient times he names the development of geometry. Coming after a
vast interval to the fourteenth century A. D., we find the mariner's
compass, and in the fifteenth the printing press, both of which beyond
question are of the same character and rank as alphabetic writing. From
the sixteenth century we get no physical invention or discovery of
leading importance, but it witnessed an amazing movement of the human
mind, which in good time gave rise to the great catalogue of advances
of the seventeenth century. To this he credits the invention of the
telescope, and, though not of equal rank, the barometer and thermometer
(which he classes as one discovery), and in other fields the discovery
of the differential calculus, of gravitation, of the laws of planetary
motion, of the circulation of the blood, and the measurement of the
velocity of light. To the eighteenth century he refers the more
important of the earlier steps in the evolution of the steam engine
and the foundation of both modern chemistry and electrical science.
This completes the list. To the above many would add Jenner's discovery
of vaccination and probably several others. Each writer, in making up
such a list, would be governed in a measure by his personal range of
studies, but no one would be likely to deviate widely from the above
list.
[=Great Discoveries of the Nineteenth Century=]
Now what has been the record since 1800? How does the nineteenth
century compare with its predecessors? In Wallace's view it is not to
be compared, as regards scientific progress and discovery, with any
single century, but with all past time. In fact, it far outstrips the
entire progress of mankind in the ages preceding 1800.
Estimating on the same basis as that which he previously adopted,
Wallace finds twenty-four discoveries and inventions of the first class
that have had their origin in the nineteenth century, against the
fifteen enumerated from all previous time.
Of the same rank with Newton's theory of gravitation, which comes from
the seventeenth century, stands out the doctrine of the correlation
and conservation of forces, one of the widest and most far reaching
generalizations that the mind of man has yet reached. Against Kepler's
laws of planetary motions from the seventeenth century we can set the
nebular theory of the nineteenth. The telescope of the seventeenth is
matched by the spectroscope of the nineteenth. If the first reveals to
us myriads of suns, otherwise unseen, scattered through the illimitable
fields of space, the second tells us what substances compose these
suns and maintain their distant fires, and, most wonderful of all,
the direction and the rate in which each is moving. Harvey's immortal
discovery of the seventeenth century finds a full equivalent in the
germ theory of disease of the nineteenth. The mariner's compass of
the fourteenth century easily yields first place to the electric
telegraph of the nineteenth, while the barometer and thermometer of the
seventeenth century are certainly less wonderful, though perhaps not
less serviceable, than the telephone and phonograph and the Röntgen
rays of our own day.
[=Useful and Scientific Steps of Progress=]
We may more briefly enumerate the remaining discoveries cited by
Wallace, partly, as will be perceived, mechanical, but mainly results
of scientific research. Early in the century came the inestimable
inventions of the railway engine and the steamboat, and somewhat later
the minor but highly useful discoveries of the lucifer match and of gas
illumination. These were quickly followed by the wonderful discovery of
photography, than which few things have added more to the enjoyment of
man. Equally important in relation to his relief from suffering are
the remarkable discoveries of anæsthetics and the antiseptic method in
surgery. Another of the great discoveries of the age is that of the
electric light, with its remarkably rapid development and utilization.
More purely scientific in character are Mendeljeff's discovery of the
periodic law in chemistry, the molecular theory of matter, the direct
measurement of the velocity of light, and the remarkable utility of
floating dust in meteorology. The list concludes with the geological
theory of the glacial age, the discovery of the great antiquity of
man, the cell theory and the doctrines of embryological development,
and last, but, in pure science, perhaps the greatest, Darwin's famous
theory of organic evolution--developed by Spencer into universal
evolution.
It is quite possible that other nineteenth century scientists would
be tempted to expand this list, and perhaps add considerably to
Wallace's twenty-four epoch-making discoveries. Indeed, since his book
was written, a twenty-fifth has arisen, in the discovery of wireless
telegraphy, the scientific marvel of the end of the century, too young
as yet for its vast possibilities to be perceived. We might also
mention the electric motor and liquid air as of equal importance with
some of those enumerated.
[=Foster's Views on Recent Progress=]
An interesting review of the advances made in science during the
nineteenth century was offered by Sir Michael Foster, President of the
British Association in its 1899 meeting, from which we may quote. He
first touched upon chemistry. The ancients, he said, thought that but
four elements existed--fire, air, earth, and water. Anything like a
correct notion of the composition of matter dates from the latter part
of the eighteenth century, when Priestley and Lavoisier revealed to the
world the nature of oxygen, and thus led to a long series of fruitful
discoveries.
The whole history of electricity as a servant of man is confined to the
last sixty or seventy years, and really springs from Volta's invention
of the galvanic battery. Frictional electricity had long been known,
but nothing beyond curious laboratory experiments were conducted
with it. The investigations and discoveries of Oersted and Faraday,
which made possible the telegraph, dynamo, trolley car and telephone,
followed Volta's discovery of the means of producing a steady current
of electricity--first announced in 1799.
Geology, too, he states to be a new born science. Although numerous
ingenious theories were entertained in regard to the origin and
significance of the strata rock, it was only at the close of the
eighteenth century that men began to recognize that the earth's crust,
with its various layers of rock, was a vast book of history, each leaf
of which told of periods of thousands or millions of years. The slow
processes of formation, and the embedding of the remains of the animal
and vegetable life of those ancient times, were only interpreted aright
after Hutton, Playfair and Cuvier had wrestled with the problem.
[=Headlights of Progress=]
With these interesting views of prominent scientists, we may proceed
to a more detailed consideration of the scientific triumphs of the
century. To present anything other than the headlights of its progress,
in the space at our command, would be impossible, in view of the
extraordinary accumulation of facts made by its many thousands of
observers, and the multitude of generalizations, of the most varied
character, offered by the thinkers in the domain of science. These
generalizations vary in importance as much as they do in character.
Many of them are evidently temporary only, and must fall before the
future progress of discovery; others are founded upon such a multitude
of significant facts, and are of such inherent probability, that they
seem likely to be as permanent as the theories of Galileo, Kepler,
Newton, and others of the older worthies.
[=Discoveries in Astronomy=]
Beginning with astronomy, the oldest and noblest of the sciences, we
could record a vast number of minor discoveries, but shall confine
ourselves to the major ones. Progress in astronomy has kept in close
pace with development in instruments. The telescope of the end of the
century, for instance, has enormously greater space-penetrating and
star-defining powers than that used at the beginning, and has added
extraordinarily to our knowledge of the number of stars, the character
of their groupings, and the constitution of solar orbs and nebulæ.
These results have been greatly added to by the use of the camera in
astronomy, the photograph revealing stellar secrets which could never
have been learned by the aid of the telescope alone. This has also the
great advantage of placing on record the positions of the stars at any
fixed moment, and thus rendering comparatively easy the detection of
motions among them.
[=Revelations of the Spectroscope=]
But it is to a new instrument of research, the spectroscope, that
we owe our most interesting knowledge of the stars. This wonderful
instrument enables us to analyze the ray of light itself, to study the
many lines by which the vari-colored spectrum is crossed and discover
to what substances certain groups of lines are due. From studying with
this instrument the substances which compose the earth, science has
taken to studying the stars, and has found that not only our sun, but
suns whose distance is almost beyond the grasp of thought, are made
up largely of chemical substances similar to those that exist in the
earth. A second result of the use of this instrument has been to
prove that there are true nebulæ in the heavens, masses of star dust
or vapor not yet gathered into orbs, and that there are dark suns,
great invisible orbs, which have cooled until they have ceased to
give off light. A third result is the power of tracing the motions
of stars which are passing in a direct line to or from the earth. By
this means it has been found that many of the double or multiple stars
are revolving around each other. A late discovery in this direction,
made in 1899, is that the Polar star, which appears single in the most
powerful telescope, is really made up of three stars, two of which
revolve round each other every four hours, while the two circle round a
more distant companion.
[=New Facts in the Solar System=]
Late astronomy has revealed to us many marvels of the solar system.
Before the nineteenth century it was not known that any planetary
bodies existed between Mars and Jupiter. On the first day of the
century--January 1, 1801--Ceres, the first of the asteroids or
planetoids, was discovered. Three others were soon discovered, and
later on smaller ones began to be found in multitudes, so that by the
end of the century not less than four hundred and fifty of these small
planetary bodies were known. Of other discoveries we may briefly refer
to the new facts discovered concerning comets and meteors, planets and
satellites, the condition of the sun's surface, the detailed knowledge
of the surface conditions of Mars and the Moon, the character of
Saturn's rings, the discovery of the planet Neptune etc., all due to
nineteenth century research.
[=The Advance of Chemistry=]
In the group of sciences known under the general title of
Physics--chemistry, light, heat, electricity, and magnetism--the
progress has been equally decided and many of the discoveries of almost
startling significance. Chemistry, as it exists to-day, is almost
wholly a child of the century. Many chemical substances were known
in the past, but their number sinks into insignificance as compared
with those of late discovery. Of chemical conceptions of earlier
date, Dalton's theory of atoms is the only one of importance that
still exists. The view long maintained--until late in the nineteenth
century, in fact--that organic and inorganic chemistry are separated
from each other by a wide gap, is no longer held. Hundreds of organic
substances, some of them of great complexity, have been made in the
chemist's laboratory, and can now be classed as properly with inorganic
as with organic substances. The gap has been closed, and there is now
but one chemistry. Only the most intricate chemical compounds still lie
beyond the chemist's grasp, and the isolation of these may be at any
time overthrown. Organic chemistry has become simply the chemistry of
carbon-compounds.
[Illustration: BARON F. H. ALEXANDER VON HUMBOLDT.
LOUIS AGASSIZ.
CHARLES DARWIN.
THOMAS H. HUXLEY.
ILLUSTRIOUS MEN OF SCIENCE, 19TH CENTURY]
[Illustration: PASTEUR IN HIS LABORATORY
The discovery of the mission of the exceedingly minute
organisms known as bacteria in producing disease ranks
among the greatest and most beneficient of our age.
By it the art of the physician was first raised to
the rank of a science. The honor of this discovery
belongs to Louis Pasteur, the eminent French chemist
and biologist.]
One chemical theory of recent date, the vortex atom theory of Lord
Kelvin, has quickly met its fate, being abandoned by its author
himself, but the study of it has been rich in results. It is now
widely held that the universe is made up of two great basic elements,
ether and matter, or perhaps one only, since it seems highly probable
that the atom of matter is a minute, self coherent mass of ether. It
is further held as doubtful that atoms ever exist alone, they being
combined by their attractions into small bodies known as molecules,
which are in incessant motion, and to whose activity the physical force
of the universe is largely due.
One of the most important chemical discoveries of the century was
that of the "periodic law" of the chemical elements, advanced by the
Russian scientist Mendeljeff, under which the weights of the atoms of
the elements were for the first time placed in harmony with each other,
and a fixed numerical relation shown to exist between them. We may
conclude this brief glance at the science by mention of the very high
temperature which the electric furnace has now placed at the command of
chemists, and the equally great refrigeration now attainable, by which
the air itself can easily be liquified and even frozen into a solid
mass.
[=Light and Its Phenomena=]
Light, naturally one of the earliest of the phenomena of nature to
attract the attention of man, was little understood until after the
advent of the nineteenth century. It was of old supposed to be a
substance of so rapid motion as to be practically instantaneous in its
movement through space. Even Newton looked upon it as a substance given
off by shining bodies, and it remained for Young, in the beginning of
the nineteenth century, to prove that light is not a substance but a
motion, a series of rapid waves or undulations in a substance extending
throughout space, and known as the lumeniferous ether. The idea
that light is instantaneous in its motion also vanished when Roemer
discovered, by observing the eclipses of Jupiter's moons, that it takes
about eight minutes for the ray of light to travel from the sun to
the earth. A cannon ball moving at the rate of 1,700 feet per second
would take about nine years to make the same journey, the wave of light
traveling at the extraordinary speed of over 186,000 miles in a second.
Yet immensely rapid as is this rate of movement, we do not need to go
to the sun and planets to measure the speed of light, but can now do
so, by the use of delicate instruments, on a few miles of the earth's
surface. This is one of the great discoveries enumerated by Wallace.
[=Late Discoveries in Optics=]
The discoveries in relation to the constitution and characteristics
of light made during the century have been so numerous that we must
confine ourselves to those of major importance. Much might be said
about the phenomena of polarization, refraction, diffraction,
photography, and the development of the power of lenses, to which the
great advance in telescopic and microscopic observation is due. Among
these steps of progress perhaps the most interesting is the development
of instantaneous photography, a striking result of which is the power,
by aid of photographs taken in rapid succession, of portraying objects
in motion--living pictures, as they are called--an exhibit now so
common and so marvelous. But among all the advances in the science
of optics the most important are spectrum analysis and the Röntgen
ray. The remarkable discoveries made in astronomy by the former of
these have been already stated. The Röntgen ray, which has the power
of rendering ordinarily opaque substances transparent, has become
of extraordinary value in surgery, as showing the exact location of
foreign substances within the body, the position and character of bone
fractures, etc.
[=Heat as a Mode of Motion=]
Heat, once looked upon as a substance, and known by the now obsolete
name of Caloric, has been demonstrated to be, like light, a motion,
the incessant leaping about of the molecules of matter, this motion
being readily transferable from one substance to another, and forming
the great substratum of power in the universe. This theory, first
promulgated by Count Rumford, an American by birth, was fully worked
out by others, and put in popular form by Professor Tyndall, an English
scientist, in his "Heat Considered as a Mode of Motion," published
in 1862. Radiant heat is identical with light, being a vibration of
the ether. It may be further said in relation to heat phenomena that
remarkable power in producing very high and extremely low temperatures
is now possessed. By the former the most refractory substances may be
vaporized. By the latter the most volatile gases may be liquified and
even frozen. The point of absolute zero, that in which all heat motion
would disappear, is estimated to be at the temperature of 274 degrees 6
minutes centigrade below the freezing point of water. A degree of cold
within some forty degrees of this has been reached in the liquefaction
of hydrogen. In 1889 the climax in this direction was reached in the
reduction, by Professor Dewar, of the very volatile element hydrogen to
the solid state.
[=Conservation and Correlation of Forces=]
Electricity, formerly, like heat and light, looked upon as a substance,
is now known to be a motion, being, in fact, identical in origin with
light and radiant heat. All these forces are considered to be motions
of the lumeniferous ether, their principal distinction being in length
of wave. In fact, it is easy to convert one of them into the other, and
the great doctrine of the conservation and correlation of forces means
simply that heat, light and electricity may be mutually transformed,
and that no loss of motion or force takes place in these changes
from one mode of motion to another. In the operation of the electric
trolley car, to offer a familiar example, the heat power of coal is
first transformed into engine motion, then into electricity, then
again into light and heat within the car, then into mass motion in the
motor, and finally passes away as electricity. No better example of the
"correlation of forces" than this familiar instance could be adduced.
[=Applications of Electricity=]
As regards the nature of electricity, though innumerable observations
have been made during the nineteenth century and a vast multitude of
facts put upon record, we know little more than is above stated. But
if we turn to the practical applications of electric power, it is to
find these standing high among the great advances of the century. To
it we owe the highly important discoveries of the telegraph and the
telephone; the conversion of engine power into electricity by the
dynamo and the use of this in moving cars, carriages and machinery; the
storage battery, with its similar applications; the use of electricity
in lighting and heating, the latter remarkably exemplified in the
electric furnace, which yields the highest temperature known on the
earth; the welding of metals by electricity; the electrotype and
electro-plating; the conversion of water power into electric force and
its transportation by wire for long distances; the therapeutic uses of
the electric current, and other applications too numerous to mention.
[=The Principles of Magnetism=]
In regard to the magnet, the handmaid of electric power, we know
little other than that the force displayed by it seems to be a result
of some mode of rotation in the atoms or molecules of matter, since
all the effects of magnetism can be produced by the rotary motion of
the electric current in spirals of wire. From this it is thought that
the molecular motion to which magnetism is due may be of an electric
character, though the permanence of the magnetic force renders this
very doubtful. It seems most probable that magnetism is a result of
some special condition of the ordinary, inherent motions of atoms--not
their fluctuating heat activities, but those fixed motions upon which
their organization and persistence depend. The readiness with which
soft iron can be magnetized and demagnetized by the use of the electric
current is of extraordinary value in the practical applications of
electricity. To this fact we owe the dynamo and the electric motor,
with all their varied uses.
With this passing glance at the physical forces, we may proceed to the
consideration of the great science of geology, which, as above stated
by Foster, is a new-born science, almost wholly of nineteenth century
development. Geology as it now exists may be said to date from 1790,
when William Smith published his "Tabular View," in which he showed
the proper succession of the rock strata and pointed out that each
group of rocks is marked by fossils peculiar to itself. With his work
began that great series of close observations which still continue, and
which have laid the constitution of the earth's crust open before us in
many of its intimate details.
[=Progress in Geology=]
Among the many geologists of the century Sir Charles Lyell stands
prominent, his "Principles of Geology" (1830-33) forming an epoch
in the advance of the science. Before his time the seeming breaks
in the series of the rocks were looked upon as the results of
mighty catastrophes, vast upheavals or depressions in the surface,
which worked widespread destruction among animals and plants, these
cataclysms being followed by new creations in the world of life. Lyell
contended that the forces now at work are of the same type as those
which have been always at work; that catastrophes have always been
local, as they are now local; that general forces have acted slowly,
and that there has been no world-wide break, either in rock deposits or
the progress of human beings.
His views gave rise to a conception of the unbroken continuity of
organic life which was greatly strengthened by the publication of
Charles Darwin's "Origin of Species," which went far to do away with
the old belief that each new life-form has arisen through special
creation, and to replace it by the theory now widely held that all
new forms of life arise through hereditary descent, with variation,
from older forms. In this conception we have the basis of the recent
theory of evolution, so thoroughly worked out and widely extended since
Darwin's time--a theory including the doctrine that man himself is a
result of descent, and not of special creation.
[=The Nebular and Meteoric Hypotheses=]
With geology is closely connected the Nebular Hypothesis of Kant
and Laplace, of eighteenth century origin, to the effect that all
the spheres of space originated in the condensation and rotation of
immense volumes of nebulous vapor, similar to the nebulæ now known to
exist in the heavens, and that each planet began its existence as a
great gaseous globe, its evolution being due to the gradual process of
cooling and condensing, by which its surface, and perhaps its whole
mass, were in time converted into solid matter. This interesting
doctrine of world evolution does not remain unquestioned. A new
hypothesis was advanced by Professor Lockyer in the final decade of the
nineteenth century, to the effect that spheral evolution is not due to
the condensation of gaseous nebulæ, but of vast aggregations of those
meteoric stones with which space seems filled, and which are drawn
together by their mutual attractions, become intensely heated through
their collisions, and are converted into liquids and gases through the
heat thus evolved. It is possible that the visible nebulæ, like the
comets, are great volumes of such meteors. This is the meteoric theory
referred to in Wallace's category of great discoveries. It is still,
however, far from being established.
[=The Science of Meteorology=]
Meteorology, the study of the atmosphere and its phenomena, is another
science to which much attention was given during the century under
review. A vast number of facts have been learned concerning the
atmosphere, its alternations of heat and cold, of calm and storm, of
pressure, of diminution of density and loss of heat in ascending, and
of its fluctuations in humidity, with the variations of sunshine and
cloud, fog, rain, snow, hail, lightning and other manifestations.
The study of the winds has been a prominent feature in the progress of
this science, and our knowledge of the causes and character of storms
has been greatly developed. The theory that storms are due to great
rotary movements in the atmosphere, immense cyclonic whirls, frequently
followed by reverse, or anti-cyclonic, movements, has gone far to
clear up the mystery of the winds, while the destructive tornado, the
terrific local whirl in the winds, has been closely studied, though not
yet fully understood. These close observations of atmospheric changes
have given rise to the Weather Bureau, by which the kind of weather to
be looked for is predicted for the United States. Similar observations
and predictions have been widely extended among civilized nations. This
is a practical application in meteorology which has been of immense
advantage, particularly in the field of navigation.
[=Progress in the Biological Sciences=]
Of the sciences with which the nineteenth century has had much to do,
those relating to organic life, classed under the general title of
biology, stand prominent, which includes botany and zoology. Subsidiary
to these are the sciences of anatomy, physiology, embryology,
psychology, anthropology, and several others of minor importance. We
have, here laid out before us a very large subject, which has made
remarkable progress during the past hundred years, much too great to
handle except in brief general terms.
In botany and zoology alike, the development of the cell theory is
one of the most conspicuous advances of the century. It has been
shown clearly that all plants and animals are made up of minute
cells, semi-fluid in consistency, and principally made up of a
highly organized chemical compound known as protoplasm, which Huxley
has denominated the "physical basis of life." These cells are the
laboratories of the system. Motions and changes take place within them.
They increase in size and divide in a peculiar manner, thus growing
in number. Many of them have self-motion like that of the low forms
known as amoebæ. Various chemical substances are elaborated in them,
such as the osseous structure of animals, the wood-fibre of plants, and
others which are given off into the sap or the blood. In short, they
are the foundation stones of life, and the physical operations of the
highest beings are made up of the combined and harmonized activities of
these myriads of minute cells.
[=Classification of Plants and Animals=]
It would be impossible, unless we should devote a volume to the
subject, to do justice to the progress of botany and zoology in the
nineteenth century. This progress consists largely in observation and
description of a vast multitude of varied forms, with the consequent
study of their affinities, and their classification into family groups,
ranging from species and varieties to orders and classes, or from
minor and local to major and general groups. Both plants and animals
have been divided up into a number of great orders, ranging in the
former instance from the microscopic bacteria to the great and highly
organized exogens, and in the latter from the minute unicellular forms
to the mammalia. We have here, aside from the cell-theory, and the
great progress in classification, nothing of epoch-making significance
to offer, and are obliged to dismiss these subjects with this brief
retrospect.
[=Division of the Cell=]
There are, however, two fields in which an important accumulation of
facts in reference to organic life has been made, those of embryology
and palæontology. The study of the organic cell by the microscope is
one of the basic facts of embryology, since living operations take
place within this cell. The network of minute fibres, of which it is
largely made up, is seen to gather into two star-shaped forms with a
connecting spindle of fibres, the division of which in the centre is
followed by the division of the cell into two. This is the primary
fact in reproduction, new cells being thus born. In higher production
two cells, arising from opposite sexes, combine, and their growth and
division give rise to the organs and tissues of a new living being. It
is the development of these organs and tissues that constitutes the
science of embryology.
[=The Sciences of the Embryo and the Fossil=]
The observation, under the microscope, of the stages of this
development, has been of the highest value in the study of animal
origin, and has aided greatly in the classification of animals. Many
old ideas died out when it was clearly shown that all life begins in a
single cell, from which the organs of the new being gradually arise.
The most important lesson taught by embryology is that the embryo
in its development passes through various stages of its ancestry,
resembling now one, now another, of the lower animals, and gains for a
brief time organs which some of its ancestors possessed permanently.
Of these facts the most significant is that the embryo of man develops
gill-slits like those which the fish uses in breathing. These are of
no use to it and soon disappear, but their appearance is very strong
evidence that the fish form lay in the line of man's ancestry, and that
man has developed through a long series of the lower animals.
In palæontology, or the study of fossil forms of animals and plant
life, we have the embryology of races as contrasted with that of
individuals. The study of the multitude of these forms which has been
collected within the past century has enabled man to fill many of the
gaps which formerly appeared to divide animal forms, and has furnished
very strong arguments in favor of the descent of new species from older
ones. One of the most striking of these facts is that in relation to
the horse, of which a practically complete series of ancestral forms
have been found, leading from a small five-toed animal, far back in
geological time, through forms in which the toes decrease in number
and the animal increases in size until the large single-toed horse is
reached.
Two other organic sciences, those of anatomy and physiology, have
added enormously to our knowledge of animated nature. Anatomy, which
is of high practical importance from its relation to surgery, is a
science of ancient origin, many important facts concerning it having
been discovered by the physicians of old Greece and Rome. This study
continued during later centuries, and by the opening of the nineteenth
the gross anatomy of the human frame was fairly well known, and many
facts in its finer anatomy had been traced. In later anatomical work
the microscope has played an active part, and has yielded numbers of
important revelations.
[=Comparative Anatomy=]
What is known as comparative anatomy has formed perhaps the most
important field of nineteenth century study in this domain of science.
Though this branch of anatomical study is as old as Aristotle, little
was done in it from his time to that of Cuvier, who was the founder
of the science of palæontology, and the first to show that the forms
and affinities of fossil forms could be deduced from the study of
existing animals. If a fossil jaw were found, for instance, with the
teeth of a ruminant, it could be taken for granted that it came from
an animal whose feet had hoofs instead of claws. It is often said that
Cuvier could construct an animal from a single bone, and though this is
saying much more than the facts bear out, he did make some marvelous
predictions of this kind.
[=Predictions Concerning Fossil Animals=]
A notable triumph of the science of comparative anatomy was the
prediction made by Cope, Marsh, and Kowalewsky, from the fact that
specialized forms are preceded by others of more generalized
structure, that an animal must once have existed with affinities, on
the one hand, with hoofed animals, and on the other with the carnivores
and the lemurs. This prediction was fulfilled in the discovery of the
fossil Phenacodus in the Eocene deposits of the western United States.
The study of comparative anatomy, particularly in its application to
fossil forms, has aided greatly in the acceptance of the doctrine
of evolution, and has been specially valuable in classification, as
showing how nearly animals are related to each other. To classify
animals and plants, in short, may be simply stated as a method of
sorting them over and placing together those which have similar
characters, just as in arranging a library we keep together books which
relate to similar subjects. We may, for instance, make one general
branch of history, a smaller branch of American history, and yet others
relating to states, to counties, to cities and towns, and, most special
of all, to particular families.
[=Discoveries in Physiology=]
The science of physiology differs from that of anatomy in dealing
with the functions of life instead of with its forms. The study of
these functions has gone on for many centuries, covering the various
operations of motion, nutrition, respiration, nervous action, growth,
and reproduction, with the many minor functions included under these.
Though many of the facts of physiology were discovered in earlier
centuries, the scientists of the nineteenth have been busy in adding
to the list, and a number of important discoveries have been made.
Prominent among these is that of anæsthesia, the discovery that by the
inhalation of certain gases a state of temporary insensibility can be
produced, lasting long enough to permit surgical and dental operations
to be performed without pain; and that of antiseptical surgery, in
which, by the employment of other chemical substances, wounds can be
kept free from the action of deleterious substances, and surgical
operations be performed without the perils formerly arising from
inflammation,--the disease--producing germs and poisons being kept out.
[=Living Threads of the Brain=]
One of the great gains of the century, says Sir Michael Foster, from
whom we have already quoted, is in our insight into nervous phenomena.
"We now know that what takes place along a tiny thread we call a nerve
fibre differs from that which takes place along its fellow threads;
that differing nervous impulses travel along different nerve fibres;
and that nervous and psychical events are the outcome of the clashing
of nervous impulses as they sweep along the closely woven web of living
threads, of which the brain is made. We have learned by experiment and
observation that the pattern of the web determines the play of the
impulses; and we can already explain many of the obscure problems, not
only of nervous disease, but of nervous life, by an analysis, tracking
out the devious and linked paths of the nervous threads."
[=Brain Surgery=]
This observation links together the sciences of physiology and
psychology, the latter the science of mental phenomena, the exact
study of which largely belongs to the nineteenth century. Broad as
this subject is, and much as has been done in it, few facts stand out
with sufficient distinctness to call for special mention here. The
most famous psychical experiments are those made on the brains of some
of the animals below man, and especially on that of the monkey, by
which the functions of the several sections of the brain have been to
some extent mapped out, the important fact being discovered that each
function is confined to a fixed locality in the brain, and with it the
accordant fact that certain regions of the brain control the muscular
movements of certain parts of the body. In consequence, a particular
affection of the hand, foot, or other region has often been traced to a
diseased condition of some known part of the brain, and the trouble has
been removed by a surgical operation on that organ.
[=The Study of Man's Past=]
The sciences last named refer specially to man, in whom they have been
particularly studied. Other sciences relating to him exclusively are
those of ethnology and anthropology, which belong almost solely to the
nineteenth century. Ethnology, the study of the races of mankind, has
been carefully and widely studied, and though the problems relating to
it have not yet been solved, a very fair conception has been gained of
the diversities and relations of mankind. Anthropology, embracing, as
it does, archæology, has been prolific in discoveries. Archæological
research has laid out before us the pathway of man through the ages
and shown his gradual and steady development, through the successive
periods of chipped stone and polished stone implements, of bronze
and iron tools and weapons, with his gradual development of pottery,
ornament, art, architecture, etc.
The most striking and notable fact in anthropological science is the
total reversal of our ideas concerning the length of time man has
dwelt upon the earth. The old limitation to a few thousand years,
everywhere held at the beginning of the century, fails to reach back
to a time when, as we now know, man had reached a considerable degree
of civilization. Back of that we can trace him by his tools and his
bones through a period many times more distant, leading back to the
glacial age of geology and possibly to a much more remote era. Instead
of man's residence upon the earth being restricted to some 6,000 years,
it probably reached back not less than 60,000, and possibly to a much
earlier period.
[=Development of the Science of Medicine=]
Among the minor sciences, there is one that has deserved that name
only within the past thirty or forty years, the science of medicine.
Formerly it was an art only, and by no means a satisfactory one.
Nothing was known of the cause of the most virulent and destructive
diseases--the infectuous fevers, the plague, cholera, etc. And the
treatment of these, and in fact of nearly all diseases, was wholly
empirical, depending solely upon experiment, not at all upon scientific
principles. Experience showed that certain drugs and chemical compounds
produced certain effects upon the system, and upon this physicians
depended, with no conception of the cause of diseases and little
knowledge of the physiological action of medicines.
[=Pasteur and His Discoveries=]
This state of affairs was materially changed during the final third
of the nineteenth century, as the result of an extensive series of
observations, set in train in great part by Louis Pasteur, Professor
of chemistry at the Sorbonne in Paris, who was in large measure the
originator of the germ theory of disease. The discovery that the
fermentation which produces alcohol is due to a microscopic organism,
the yeast-plant, gave Pasteur the clue, and he soon was able to prove
that other fermentations,--the lactic, acetic, and butyric,--are also
due to the action of living forms. It had further been found that the
putrefaction of animal substance was caused in the same way, and it has
since been abundantly demonstrated that if these minute organisms can
be kept out of animal and vegetable substances these may be preserved
indefinitely. This fact has given rise to one of the most important
industries of the century, the keeping of fruits, meats, etc., by the
process of air-tight canning.
Pasteur next extended his observations to the silkworm, which was
subject to an epidemic disease that had almost ruined the silk industry
in France. Others before him had discovered what were supposed to be
disease germs in the blood of these worms. He proved positively that
these bacteria, as they are called, are the cause of the disease, and
that infection could be prevented by proper precautions. From the
insect Pasteur proceeded to the higher animals, and investigated the
cause of splenic fever, a dangerous epidemic among farm cattle. This
he also proved to be caused by a minute form of life, and that fowl
cholera is due to still another form of micro-organism. At a later date
he studied hydrophobia, which he traced to a similar cause, and for the
cure of which he established the Pasteur Institute in 1886.
This was not the whole of Pasteur's work. He discovered not only the
cause of these diseases, but a system of vaccination by which they
could be cured or prevented. By "cultivating" the bacteria in various
ways, he succeeded in decreasing their dangerous properties, so that
they would give the disease in a mild form,--acting in the same way as
vaccination does in the case of small-pox, by enabling the animals to
resist virulent attacks of the disease.
[=Koch and the Comma Bacillus=]
Pasteur's work was performed largely on the lower animals. Others have
devoted themselves to the infectuous diseases which attack the human
frame, and with remarkable success. Robert Koch, a German physician,
applied himself to the study of cholera, which he proved in 1883 to
be due to a germ named by him, from its shape, the comma bacillus. He
discovered about the same time the bacterial organism which causes the
fatal disease of tuberculosis, or consumption. Other investigators have
traced typhoid and yellow fevers, diphtheria, and some other infectuous
diseases to similar causes, and the study of diseases of this character
has at last gained the status of a science.
Methods of cure are also becoming scientific. These minute organisms,
once introduced within the body, tend to increase in number at an
amazing rate, feeding on the blood and tissues, and giving off
substances called toxines which in some cases are of highly poisonous
character. To overcome their effect inoculation of anti-toxines is
practiced. These are yielded by the same bacteria as produce the
toxines, and inoculation with them enables the system to resist the
action of the toxin poisons.
[=Antiseptic Surgery=]
We must dismiss this broad subject with this brief consideration,
saying further that it is still largely in the stage of experiment, and
that many of its theories must be left to the twentieth century for
proof. Its study, however, has been of inestimable value in another
direction, that of antiseptic surgery, a mode of treatment of surgical
wounds introduced by Sir Joseph Lister, and now used by all surgeons
with the most beneficial effects. It being recognized that inflammation
and putrefactive action in wounded tissues are due to the action of
disease germs introduced by the air or by the hands and instruments of
the operators, the greatest care is now taken, by the use of chemical
substances fatal to those germs, to prevent their entrance. As a result
many diseases once common in hospitals--pyæmia, septicæmia, gangrene
and erysipelas--have almost disappeared, fever and the formation of
pus are prevented, and healing is rapid and continuous, while surgeons
now daringly and successfully undertake operations in the most secret
recesses of the body, which formerly would have led to certain death.
[=The Science of Hygiene=]
A secondary result of the germ theory of disease is the great advance
in hygiene, which, formerly almost non-existent, has now reached the
status of a science. It is still against these perilous germs that
continuous battle is kept up, absolute cleanliness being the ultimatum
at which physicians aim. Disease germs lurk everywhere, and can only
be combatted by incessant care. The bacteria of cholera and typhoid
fever, for example, are known to be conveyed in water, and the former
epidemics of these diseases were in great measure due to the free
use of polluted water for drinking. Their ravages have been largely
arrested by boiling, filtering or otherwise purifying drinking water,
while the free use of carbolic acid and other antiseptics in hospitals
has put an end to the reign of infection which once made those places
hives of disease.
We may fitly conclude this chapter with reference to a subject several
times referred to in its pages, and which is looked upon as the
greatest scientific theory of the century, that of evolution. The
belief that new species of animals and plants arise through development
from older ones is not of recent origin, but is at least as old as
Aristotle. It was taught by Harvey, Erasmus Darwin, Goethe, and
others in the eighteenth century, but the first attempt to develop a
general theory of organic evolution was made by Lamarck, in the early
part of the succeeding century. Lamarck's view, however, that the
variations in animals are the result of efforts on their part to gain
certain results,--the neck of the giraffe, for instance growing longer
through its attempt to browse on leaves just out of reach,--did not
gain acceptance, and it was not until after the middle of the century
that a more satisfactory theory was presented.
[=Darwin and Natural Selection=]
The theory of evolution, as now understood, was arrived at
simultaneously by Alfred Russell Wallace and Charles Darwin, it being
fully worked out by the latter in his "Origin of Species by Means of
Natural Selection," published in 1859. This theory--that the changes in
animals are due to the struggle for existence among vast multitudes,
and the survival of those whose natural variations in form give them
an advantage over their fellows in the battle of life--is now accepted
by the great body of scientists, while the general idea of evolution
has been extended to cover all changes in the universe, inorganic as
well as organic. This extension has been the work of Herbert Spencer
and many other scientific and philosophical writers, and no domain
of nature is now left outside of the range of evolutionary forces.
The argument which makes man himself a result of evolution, and not a
product of special creation, was the final one presented by Darwin,
and has given point to a multitude of observations in the science of
anthropology made since his day.
[Illustration: BROWNING
WORDSWORTH
TENNYSON
SHELLEY
AUSTIN
THE GREAT POETS OF ENGLAND]
[Illustration: JAMES R. LOWELL
WILLIAM CULLEN BRYANT
OLIVER W. HOLMES
H. W. LONGFELLOW
RALPH WALDO EMERSON
JOHN G. WHITTIER
SIX GREAT AMERICAN POETS]