If we were to attempt to group the names associated with the study of
biology, we would find that in a general way they were connected either
with discoveries of a purely scientific nature or with the benefiting of
man's condition by the _application_ of the purely scientific discoveries.
The first group are necessary in a science in order that the second group
may apply their work. It was necessary for men like Charles Darwin or
Gregor Mendel to prove their theories before men like Luther Burbank or any
of the men now working in the Department of Agriculture could benefit
mankind by growing new varieties of plants. The discovery of scientific
truths must be achieved before the men of modern medicine can apply these
great truths to the cure or prevention of disease. Since we are most
interested in discoveries which touch directly upon human life, the men of
whom this chapter treats will be those who, directly or indirectly, have
benefited mankind.
The Discoverers of Living Matter.--The names of a number of men living at
different periods are associated with our first knowledge of cells. About
the middle of the seventeenth century microscopes came into use. Through
their use plant cells were first described and pictured as hollow boxes or
"cells." But it was not until 1838 that two German friends, Schleiden and
Schwann by name, working on plants and animals, discovered that both of
these forms of life contained a jellylike substance that later came to be
called _protoplasm_. Another German named Max Schultz in 1861 gave the name
protoplasm to _all living matter_, and a little later still Professor
Huxley, a famous Englishman, friend and champion of Charles Darwin, called
attention to the physical and chemical qualities of protoplasm so that it
came to be known as the chemical and physical basis of life.
[Illustration: Prof. Tyndall's experiment to show that if air containing
germs is kept from organic substances, such substances will not decay. The
box is sterilized; likewise the tubes (_t_) containing nutrients. Air is
allowed to enter by the tubes (_u_), which are so made that dust is
prevented from entering. A thermometer (_th_) records the temperature. The
substances in the tubes do not decay, no matter how favorable the
temperature.]
Life comes from Life.--Another group of men, after years of patient
experimentation, worked out the fact that _life comes from other life_. In
ancient times it was thought that life arose _spontaneously_; for example,
that fish or frogs arose out of the mud of the river bottoms, and that
insects came from the dew or rotting meat. It was believed that bacteria
arose spontaneously in water, even as late as 1876, when Professor Tyndall
proved by experiment the contrary to be true.
As early as 1651 William Harvey, the court physician of Charles I of
England, showed that all life came from the egg. It was much later,
however, that the part played by the sperm and egg cell in fertilization
was carefully worked out. It is to Harvey, too, that we owe the beginnings
of our knowledge of the circulation of the blood. He showed that blood
moved through tubes in the body and that the heart pumped it. He might be
called the father of modern physiology as well as the father of embryology.
A long list of names might be added to that of Harvey to show how gradually
our knowledge of the working of the human body has been added to. At the
present time we are far from knowing all the functions of the various parts
of the human engine, as is shown by the number of investigators in
physiology at the present time. Present-day problems have much to do with
the care of the human mechanism and with its surroundings. The solution of
these problems will come from applying the sciences of hygiene, preventive
medicine, and sanitation.
In the preceding chapters of this book we have learned something about our
bodies and their care. We have found that man is able within limitations to
control his environment so as to make it better to live in. All of the
scientific facts that have been of use to man in the control of disease
have been found out by men who have devoted their lives in the hope that
their experiments and their sacrifices of time, energy, and sometimes life
itself might make for the betterment of the human race. Such men were
Harvey, Jenner, Lister, Koch, and Pasteur.
[Illustration: Edward Jenner, the discoverer of vaccination.]
Edward Jenner and Vaccination.--The civilized world owes much to Edward
Jenner, the discoverer of vaccination against smallpox. Born in Berkeley, a
little town of Gloucestershire, England, in 1749, as a boy he showed a
strong liking for natural history. He studied medicine and also gave much
time to the working out of biological problems. As early as 1775 he began
to associate the disease called cowpox with that of smallpox, and gradually
the idea of inoculation against this terrible scourge, which killed or
disfigured hundreds of thousands every year in England alone, was worked
out and applied. He believed that if the two diseases were similar, a
person inoculated with the mild disease (cowpox) would after a slight
attack of this disease be immune against the more deadly and loathsome
smallpox. It was not until 1796 that he was able to prove his theory, as at
first few people would submit to vaccination. War at this time was being
waged between France and England, so that the former country, usually so
quick to appreciate the value of scientific discoveries, was slow to give
this method a trial. In spite of much opposition, however, by the year
1802, vaccination was practiced in most of the civilized countries of the
world. At the present time the death rate in Great Britain, the home of
vaccination, is less than .3 to every 1,000,000 living persons. This shows
that the disease is practically wiped out in England. An interesting
comparison with these figures might be made from the history of the disease
in parts of Russia where vaccination is not practiced. There, thousands of
deaths from smallpox occur annually. During the winter of 1913-1914 an
epidemic of smallpox with more than 250 cases broke out in the city of
Niagara Falls. This epidemic appears to be due to a campaign conducted by
people who do not believe in vaccination. In cities and towns near by,
where vaccination was practiced, no cases of smallpox occurred. Naturally
if opposition to vaccination is found nowadays, Jenner had a much harder
battle to fight in his day. He also had many failures, due to the imperfect
methods of his time. The full worth of his discovery was not fully
appreciated until long after his death, which occurred in 1823.
[Illustration: Louis Pasteur.]
Louis Pasteur.--The one man who, in biological science, did more than any
other to directly benefit mankind was Louis Pasteur. Born in 1822, in the
mountains near the border of northeastern France, he spent the early part
of his life as a normal boy, fond of fishing and not very partial to study.
He inherited from his father, however, a fine character and grim
determination, so that when he became interested in scientific pursuits he
settled down to work with enthusiasm and energy.
At the age of twenty-five he became well known throughout France as a
physicist. Shortly after this he became interested in the tiny plants we
call bacteria, and it was in the field of bacteriology that he became most
famous. First as professor at Strassburg and at Lille, later as director of
scientific studies in the Ecole Normale at Paris, he showed his interest in
the application of his discoveries to human welfare.
In 1857 Pasteur showed that fermentation was due to the presence of
bacteria, it having been thought up to this time that it was a purely
chemical process. This discovery led to very practical ends, for France was
a great wine-producing country, and with a knowledge of the cause of
fermentation many of the diseases which spoiled wine were checked.
In 1865-1868 Pasteur turned his attention to a silkworm disease which
threatened to wipe out the silk industry of France and Italy. He found that
this disease was caused by bacteria. After a careful study of the case he
made certain recommendations which, when carried out, resulted in the
complete overthrow of the disease and the saving of millions of dollars to
the poor people of France and Italy.
The greatest service to mankind came later in his life when he applied
certain of his discoveries to the treatment of disease. First experimenting
upon chickens and later with cattle, he proved that by making a virus
(poison) from the germs which caused certain diseases he could reduce this
virus to any desired strength. He then inoculated the animals with the
virus of reduced strength, giving the inoculated animals a mild attack of
the disease, and found that this made them _immune_ from future attacks.
This discovery, first applied to chicken cholera, laid the foundation for
all future work in the uses of serums, vaccines, and antitoxins.
Pasteur was perhaps the best known through his study of rabies. The great
Pasteur Institute, founded by popular subscriptions from all over the
world, has successfully treated over 22,000 cases of rabies with a death
rate of less than 1 per cent. But more than that it has been the place
where Roux, a fellow worker with Pasteur, discovered the antitoxin for
diphtheria which has resulted in the saving of thousands of human lives.
Here also have been established the principles of inoculation against
bubonic plague, lockjaw, and other germ diseases.
Pasteur died in 1895 at the age of seventy-three, "the most perfect man in
the realm of science," a man beloved by his countrymen and honored by the
entire world.
[Illustration: Robert Koch.]
Robert Koch.--Another name associated with the battle against disease germs
is that of Robert Koch. Born in Klausthal, Hanover, in 1843, he later
became a practicing physician, and about 1880 was called to Berlin to
become a member of the sanitary commission and professor in the school of
medicine. In 1881 he discovered the germ that causes tuberculosis and two
years later the germ that causes Asiatic cholera. His later work has been
directed toward the discovery of a cure for tuberculosis and other germ
diseases. As yet, however, no certain cure seems to have been found.
Lister and Antiseptic Treatment of Wounds.--A third great benefactor of
mankind was Sir Joseph Lister, an Englishman who was born in 1827. As a
professor of surgery he first applied antiseptics in the operating room. By
means of the use of carbolic acid or other antiseptics on the surface of
wounds, on instruments, and on the hands and clothing of the operating
surgeons, disease germs were prevented from taking a foothold in the
wounds. Thus blood poisoning was prevented. This single discovery has done
more to prevent death after operations than any other of recent time.
Modern Workers on the Blood.--At the present time several names stand out
among investigators on the blood. Paul Ehrlich, a German born in 1854, is
justly famous for his work on the blood and its relation to immunity from
certain diseases. His last great research has given to the world a specific
against the dread disease syphilis.
Another name associated with the blood is that of Elias Metchnikoff, a
Russian. He was born in 1845. Metchnikoff first advanced the belief that
the colorless blood corpuscles, or _phagocytes_, did service as the
sanitary police of the body. He has found that there are several different
kinds of colorless corpuscles, each having somewhat different work to do.
Much of the modern work done by physiologists on the blood are directly
founded on the discoveries of Metchnikoff.
[Illustration: Charles Darwin, the grand old man of biology.]
Heredity and Evolution. Charles Darwin.--There is still another important
line of investigation in biology that we have not mentioned. This is the
doctrine of evolution and the allied discoveries along the line of
heredity. The development or evolution of plants and animals from simpler
forms to the many and present complex forms of life have a practical
bearing on the betterment of plants and animals, including man himself. The
one name indelibly associated with the word evolution is that of Charles
Darwin.
Charles Darwin was born on February 12, 1809, a son of well-to-do parents,
in the pretty English village of Shrewsbury. As a boy he was very fond of
out-of-door life, was a collector of birds' eggs, stamps, coins, shells,
and minerals. He was an ardent fisherman, and as a young man became an
expert shot. His studies, those of the English classical school, were not
altogether to his liking. It is not strange, perhaps, that he was thought a
very ordinary boy, because his interest in the out-of-doors led him to
neglect his studies. Later he was sent to Edinburgh University to study
medicine. Here the dull lectures, coupled with his intense dislike for
operations, made him determine never to become a physician. But all this
time he showed his intense interest in natural history and took frequent
part in the discussions at the meetings of one of the student zoological
societies.
In 1828 his father sent him to Cambridge to study for the ministry. His
three years at the university were wasted so far as preparation for the
ministry were concerned, but they were invaluable in shaping his future. He
made the acquaintance of one or two professors who were naturalists like
himself, and in their company he spent many happy hours in roaming over the
countryside collecting beetles and other insects. In 1831 an event occurred
which changed his career and made Darwin one of the world's greatest
naturalists. He received word through one of his professional friends that
the position of naturalist on her Majesty's ship _Beagle_ was open for a
trip around the world. Darwin applied for the position, was accepted, and
shortly after started on an eventful five years' trip around the world. He
returned to England a famous naturalist and spent the remainder of his long
and busy life producing books which have done more than those of any other
writer to account in a satisfactory way for the changes of form and habits
of plants and animals on the earth. His theories established a foundation
upon which plant and animal breeders were able to work.
His wonderful discovery of the doctrine of evolution was due not only to
his information and experimental evidence, but also to an iron
determination and undaunted energy. In spite of almost constant illness
brought about by eyestrain, he accomplished more than most well men have
done. His life should mean to us not so much the association of his name
with the _Origin of Species_ or _Plants and Animals under Domestication_,
two of his most famous books, but rather that of a patient, courteous, and
brave gentleman who struggled with true English pluck against the odds of
disease and the attacks of hostile critics. He gave to the world the proofs
of the theory on which we to-day base the progress of the world. Darwin
lived long enough to see many of his critics turn about and come over to
his beliefs. He died on the 19th of April, 1882, at seventy-four years of
age.
Associated with Darwin's name we must place two other co-workers on
heredity and evolution, Alfred Russel Wallace, an Englishman who
independently and at about the same time reached many of the conclusions
that Darwin came to, and August Weissman, a German. The latter showed that
the protoplasm of the germ cells (eggs and sperms) is directly handed down
from generation to generation, they being different from the other body
cells from the very beginning. In 1883 a German named Boveri discovered
that the chromosomes of the egg and the sperm cell were at the time of
fertilization just half in number of the other cells (see page 252) so that
a _fertilized_ egg was really a _whole cell_ made up of _two half cells_,
one from each parent. The chromosomes within the nucleus, we remember, are
believed to be the bearers of the hereditary qualities handed down from
parent to child. This discovery shows us some of the mechanics of heredity.
Applications to Plant and Animal Breeding.--Turning to the practical
applications of the scientific work on the method of heredity, the name of
Gregor Mendel, an Austrian monk, stands out most prominently. Mendel lived
from 1822 until 1884. His work, of which we already have learned something
(see page 258), remained undiscovered until a few years ago. The
application of his methods to plant and animal raising are of the utmost
importance because the breeder is able to separate the qualities he desires
and breed for those qualities only. Another name we have mentioned with
reference to plant breeding is Hugo de Vries, the Dutchman who recently
showed that in some cases plants arise as new species by sudden and great
variations known as _mutations_. And lastly, in our own California, Luther
Burbank, by careful hybridizing, is making lasting fame with his new and
useful hybrid plants.