(1822-1895)
[Illustration: Dr. Louis Pasteur.]
Louis Pasteur, the Columbus of "the world of the infinitely
little"--to quote the phrase of Professor Dumas--was born in the
town of Dôle, France, on December 27, 1822. His father was an old
soldier, decorated on the field of battle, who, after leaving the
array, earned his bread as a tanner. In 1825 M. Pasteur moved from
Dôle to the town of Arbois, on the borders of the Cuisance, where
his son began his education in the communal college. The boy was
exceedingly fond of fishing and of sketching, and it was not until
he reached the age of fourteen that he began study in earnest. There
being no professor of philosophy at Arbois, Louis Pasteur moved to
Besançon, where he received the degree of _bachelier ès lettres_ and
was at once appointed as one of the tutors. Here he studied the
course in mathematics necessary for admission into the École
Normale, in Paris, which he entered in October, 1843. Already his
passion for chemistry had shown itself, and he took the lectures in
that science delivered by M. Dumas at the Sorbonne, and by M. Balard
at the École Normale. It was but a short time before he became a
marked man in his class, especially for his intense devotion to
experiment. Thanks to M. Delafosse, one of the lecturers of the
École Normale, his attention was turned to crystallography, and a
note from the German chemist, Mitscherlich, communicated to the
Academy of Sciences, set him on fire with curiosity. Mitscherlich
declared: "The paratartrate and the tartrate of soda and ammonia
have the same chemical composition, the same crystalline form, the
same angles, the same specific weight, the same double refraction,
and the same inclination of the optic axes. Dissolved in water,
their refraction is the same. But while the dissolved tartrate
causes the plane of polarized light to rotate, the paratartrate
exacts no such action."
Pasteur at once instituted experiments resulting in the discovery of
minute facets in the tartrate which gave it the power noted. He
found in the paratartrate these facets existed, but that there was
an equal admixture of right-and left-handed crystals, and the one
neutralized the effect of the other. He also discovered the
left-handed tartrate. These discoveries at the opening of Pasteur's
career brought him at once to the front among the scientific men. He
followed them with a profound investigation into the symmetry and
dissymmetry of atoms, and reached the conclusion that in these lay
the basic difference between inorganic and organic matter, between
the absence of life and life.
Nominated at the age of thirty-two as Dean of the Faculté des
Sciences, at Lille, Pasteur determined to devote a portion of his
lectures to fermentation. At that time ferments were believed to be,
to quote Liebig, "Nitrogenous substances--albumin, fibrin, casein;
or the liquids which embrace them--milk, blood, urine--in a state of
alteration which they undergo in contact with air." Pasteur examined
the lactic ferment and found little rods, 1/25000 inch in length,
which nipped themselves in the centre, divided into two, grew to
full length and divided again, and these living things he declared
to be the active principles of the ferment. He made a mixture of
yeast, chalk, sugar, and water, added some of the rods, and got
fermentation. He then made a mixture of sugar, water, phosphate of
potash, and magnesia, and introducing fresh cells, fermentation
followed. Liebig's theory of the nitrogenous character of the
ferment disappeared when fermentation was caused in a mixture having
no nitrogenous elements.
Pasteur had discovered that fermentation was a phenomenon of
nutrition; it followed the increase and growth of the little rods.
The next step was the discovery of the ferment of butyric acid, a
species of vibrio consisting of little rods united in chains of two
or three and possessed of movement. He found these vibrios lived
without air. Further experiments showed there were ferments to which
air was necessary, called by Pasteur the _ærobics_, and others to
whom oxygen was fatal, the _anærobics_. He proved, also, by an
exhaustive series of experiments, that what is called putrefaction
of animal matter is the result of the combined work of the _ærobics_
and the _anærobics_, which reduce that part not taken up by oxygen
to dead organic matter, ready in its turn to form food for living
things.
His attention having been turned to the needs of the vinegar makers
of Orleans, Pasteur began the examination of the ferment which
produces vinegar from wine. He found this in the mycoderm aceto, a
mould-like plant which has the power of developing acetic acid from
alcohol. As the result of his investigation, the manufacturers of
vinegar in France were able to do away with the cumbrous process
they had long followed, and to make vinegar, not only more cheaply,
but of very much better quality. But during these experiments
Pasteur found the temperature of 65° C. was sufficient to kill the
mycoderm. When, then, the wine makers of France appealed to him to
investigate the "diseases" of wine, he was ready for the work.
Before this, however, he had examined the claims of Pouchet and
others to their alleged discovery of spontaneous generation; in
other words, the production of life. Ranging himself against them,
Pasteur showed their experiments not to have been conclusive, simply
because they had not succeeded in excluding the dust which contained
germs of life in the shape of spores of microscopic plants.
The "diseases" of wine produce sour wine, wine that "spirits,"
"greasy" wine, and bitter wine. Pasteur found each to be due to a
different microscopic ferment, all of which could be killed by heat.
He placed bottles of wine in a bath heated to 60° C., and invited
the most experienced wine tasters of Paris to try them afterward.
The result of the test was the unanimous verdict that the wines had
not been injured in the least, and to-day these "diseases" of wine
are a thing of the past.
There are departments in France where the culture of the silk-worm
is the principal industry of the inhabitants. In 1849 a strange
disease, called pebrine, broke out among the worms; they were unable
to moult and died before the cocoons were spun. It spread in the
most alarming manner until, from a crop with an average of one
hundred and thirty million francs a year, the production of silk
went to less than fifty millions. The silk cultivators sent for
eggs--seed is the technical name--to Italy and Greece, and for one
season all went well. The next, the plague was as bad as ever. More
than that, it spread to Italy, Spain, Greece, and Turkey, until
Japan was the only silk-producing country where the worm was
healthy. Societies and governments, as well as individuals, were
aghast, for the silk industry of the world was on the verge of
annihilation, and every remedy the mind of man could conceive was
tried, only to be rejected. In France alone the loss in 1865 was
over one hundred million francs.
At the suggestion of Professor Dumas, the Government induced Pasteur
to examine into the "disease." He had seen in a report on the
epidemic made by M. de Quatrefages, that there were found in the
diseased worms certain minute corpuscles only to be seen under the
microscope. When in June, 1865, Pasteur arrived in the town of
Alais, he found these corpuscles without difficulty. He traced them
from the worm to the chrysalid, in the cocoon, and thence to the
moth; he found worms hatched from the eggs laid by these moths
invariably developed the corpuscles. He crushed a corpuscular moth
in water, painted a mulberry leaf with it, fed it to a healthy worm,
and the corpuscles developed. He hatched eggs from moths free from
corpuscles and secured healthy worms. While working on the
"disease," Pasteur discovered in 1867 that the mortality among the
worms was in part due to another disease, the _flacherie_, and this
he found was the result of imperfect digestion.
[Illustration: Pasteur in his Laboratory.]
_Flacherie_ was contagious, and was caused by the fermentation of the
food eaten in the body of the worm. The causes of this fermentation,
the condition of the leaves, the temperature, and others were pointed
out. As the result of five years' work, Pasteur had restored the silk
industry to its former position, and had shown that the microscopic
examination of the moth laying the eggs to be hatched was a perfect
safeguard against _pebrine_ and _flacherie_.
At the request of the emperor, Pasteur went to the Villa Vicentia,
in Austria, belonging to the prince imperial. For ten years the silk
harvest there had not paid the cost of the eggs.
Although he was just recovering from an attack of paralysis brought
on by overwork, Pasteur travelled to Austria, introduced his methods
and the sale of the cocoons gave the villa a net profit of
26,000,000 francs. No wonder it was said of him that his discoveries
alone exceeded in money value to the French people the war indemnity
paid by them to the Germans.
Splenic fever, called _charbon_ in France, had for years decimated
the flocks in France, Italy, Russia, Egypt, Hungary, and Brazil. It
attacked the horse and cow as well as the sheep, and human beings
died of it when they developed malignant pustule. Many scientific
men had studied it, but Dr. Davaine, in 1850, was the first to find
in the blood of a sheep that had died of the disease, "little
thread-like bodies about twice the length of a blood-corpuscle.
These little bodies exhibit no spontaneous motion."
Pasteur began the examination of splenic fever by securing some of
the blood from an animal dying from it. In the work before him he
associated with himself M. Joubert, one of his former pupils. A drop
of the blood sown in the water of yeast--the medium used for
cultures by Pasteur at that time--produced myriads of the rods, the
bacilli or microbes. A drop of this taken at the end of twenty-four
hours, and placed in a fresh flask of the medium, again produced
thousands of the bacilli. Pasteur found that guinea-pigs inoculated
from the first flask developed the fever, and the same result
followed when the inoculation was from the twentieth. He had proved,
then, that splenic fever was produced by the bacilli, by living
organisms only to be seen with a powerful microscope.
While working on the bacilli of splenic fever, Pasteur had isolated
the bacillus of chicken cholera, had cultivated it and had
inoculated chickens with it, developing the disease. He found that
so long as the cultures were made from flask to flask within
twenty-four hours, the virus of the disease, that is, the power of
the bacilli to produce cholera in the fowls inoculated, remained the
same and the fowl died. But he discovered that if a flask containing
the bacilli were left exposed to the air for two weeks, and the
fowls were then inoculated with bacilli from this flask, they became
sick, but did not die. Following this up, he inoculated a hen that
had recovered from a sickness so produced, with the bacilli in their
strongest and most virulent form, and the hen showed no effect
whatever. Then he took two hens, one fresh from the coop and the
other well again after the sickness produced by the inoculation with
the exposed bacilli, and inoculated both with the blood of a hen
that was dying of chicken cholera. The first died, the second was
affected. In other words, Pasteur had made the greatest discovery in
physiology of this century. He had found it is possible to attenuate
the virus of a virulent disease, and to use that virus so attenuated
as a vaccine matter which will guard the animal vaccinated against
the disease. He had taken Jenner's discovery, and proved it applied
to other diseases besides small-pox.
Pasteur's theory of the reason why any vaccine matter will have its
prophylactic effect, is this: He believes there is in the blood of
any animal subject to a disease caused by bacilli some substance
which is necessary to the sustenance of those bacilli; and when the
bacilli, having an attenuated virus, are introduced, they slowly
consume all of this substance.
The substance being one which nature creates very slowly, no
subsequent introduction of the bacilli, however virulent, can
produce the disease until such time shall have elapsed that a new
supply of the substance shall have been secreted. In this way he
accounts for the fact that vaccination will protect from small-pox
for a more or less defined period of time.
Pasteur hastened to apply his discovery of the attenuation of the
virus of chicken cholera to the virus of splenic fever. Here,
however, he was met with a serious difficulty. The microbes of
splenic fever, if left in the flask for forty-eight hours, developed
bright spots, and gradually into these spots the bacilli themselves
seemed to be absorbed. Pasteur found these spots were the spores or
seeds of the microbes, and he also found that, while the bacilli
could be killed easily in various ways, the spores possessed a much
greater resistance. They could be dried, for example, and preserved
in that state indefinitely. It was apparent that the oxygenation
which attenuated the venom of the bacilli of chicken cholera was
impossible with those of splenic fever if the bacilli of the latter
disappeared within a week, leaving the spores behind. But Pasteur
had discovered before this that, unless the temperature of a fowl
were lowered artificially, inoculation with the microbes of splenic
fever would not produce the disease. From this he argued that, as
the heat of the fowl's body was sufficient to resist the contagion,
the bacilli themselves must be extremely sensitive to variations in
temperature. He tried the experiment and found, by lowering the
temperature of the flasks containing the cultures, he could prevent
the formation of the spores. He then attenuated the venom of the
splenic bacilli as he had that of the fowl cholera, tried it on
guinea-pigs, found they became sick and recovered; inoculated them
with the bacilli of full strength, but with no result. Pursuing his
experiments, he discovered that he could by using vaccine-attenuated
bacilli, of unequal strength, cause any degree of sickness he
pleased.
In the early part of 1881 Pasteur agreed to hold a public exhibition
of his vaccine for splenic fever, the animals to be supplied by the
Society of Agriculture in Melun. The experiment was begun on May
5th. Pasteur inoculated twenty-four sheep, one goat, and six cows
with six drops each of attenuated virus, and twelve days afterward
he reinoculated them with a stronger virus. On May 31st he
reinoculated the thirty-one animals with the strongest virus of
splenic fever, and at the same time inoculated twenty-five sheep and
four cows which had not been vaccinated as were the others. On June
2d over two hundred people assembled at the farm to see the result.
The twenty-five sheep that had not been vaccinated all died before
that evening. The non-vaccinated cows had intense fever and great
swellings, and could scarcely stand up. On the other hand, the
vaccinated sheep and cows were in full health and were feeding
quietly. Pasteur had conquered splenic fever.
Having attenuated the virus of these bacilli, Pasteur began a series
of experiments to determine whether the attenuated virus could be
intensified until its former venom was obtained. This he succeeded
in, and thus discovered what is probably the key to the solution of
the problem of the periodicity of epidemics of contagious diseases,
such as cholera. In 1882 Pasteur's attention was called to a new
disease, swine fever (_rouget_), which was ravaging the herds of
swine in France. He found the microbes, attenuated them, vaccinated
the pigs, and secured the most favorable results. He also discovered
that by passing the microbe of a disease through an animal not
subject to that disease, he attenuated it so far as its effects on
another were concerned.
It was in 1880 that Pasteur first began his experiments in
hydrophobia. Securing the saliva of a child suffering from the
disease, he inoculated rabbits with it and they died in thirty-six
hours. He examined the saliva and the blood of the rabbits, and
found in both a new microbe (a minute disk having two points). He
established by repeated experiments that hydrophobia is a disease of
the nerves, that a portion of the medulla oblongata, or of the
spinal cord, is very much more certain to produce the disease, when
introduced into the blood or placed on the brain, than is the
saliva. He succeeded at last in isolating the microbe, in making
cultures of it, and then attenuating it, and in May, 1884, he
produced before a commission appointed by the Minister of Public
Instruction the following results:
Of six dogs unprotected by vaccination, three died as the results of
bites of a dog violently mad. Of eight unvaccinated dogs, six died
after extra-venous inoculation of rabic matter. Of five unvaccinated
dogs, all died after inoculation, by trepanning, of the brain with
rabic matter. Of twenty-three vaccinated dogs, not one was attacked
with the disease after inoculation, in any fashion, with the most
virulent rabic matter procurable.
During his long and busy life Louis Pasteur has been honored after
every fashion known to men. He has opened the gates of knowledge
wider than they were ever opened before, and in his discovery of the
germs of disease, and in his still more wonderful discovery of the
possibility of attenuating those germs and converting them into
vaccines, he has revolutionized all ideas of physiology. He is one
of the greatest pioneers in science that has ever lived, and his
work will make his name illustrious so long as men shall continue on
this earth. The lesson of his life is the supreme value of
experiment; for, as was once said of him by Professor Dumas,
"Pasteur is never mistaken, because he never asserts anything he
cannot show another man how to prove."
[Signature: Cyrus Edson.]