It is one of the curious features of history that genuine worth of
human accomplishment is almost in inverse ratio to the popularity it
obtains in the generation in which it is produced. Supremely great
work is rarely appreciated at anything like its proper value, by
contemporaries. This principle is true apparently in all fields of
human endeavor. In literature and in art it is a commonplace. But
also, surprising though it may be, in science and in social betterment
the rule holds a prominent place. It is nearly always the sign of only
passing merit when any work secures the plaudits of its own
generation. Brilliant theories are often immediately hailed with
universal acclaim, while ground-breaking observations that are really
great discoveries are apt to be neglected. The really new discovery is
so novel that men cannot appreciate it at once. It is so different
from their ordinary modes of thinking that they cannot place it
properly. Its complete significance fails them.
This has been true for our nineteenth century biology almost more
strikingly than for any other department of knowledge. Our many
avenues of publicity instead of heralding abroad the great
observations as soon as they have been made, in order to enable others
to continue the work that the master mind has begun, have been only
too constantly crowded with new opinions, novel theories, taking
hypotheses, all attracting attention that they did not deserve. Men
like Theodore Schwann, the father of the cell doctrine, are not apt to
be so well known as the suggestor of some {254} striking bit of
theory. Even the great biologists, such as Darwin himself, are known
rather for their insubstantial theories than for their substantial
additions to biological knowledge by patient observation and genial
penetration into the secrets of nature. It is perhaps a warning to the
modern physician who realizes this state of affairs, not to take the
popular theories even in his own branch of biology as the current coin
of truth. Theories pass, but observations endure. Auenbrugger's new
method of tapping the chest in order to elicit its varying sounds
looked even more childish than Galvani's acceptance of the position of
dancing master to a frog, but their observations thus made continued
the germs of undying truth.
While the name and the life of Theodore Schwann are but little known
by the general public, his work is very thoroughly appreciated by
those who have made special studies in biology, and few men in the
progress of that science are considered to hold as high a place as
that assigned to him. A study of the life of Schwann will serve to
show not only that he eminently deserves this honor which has come to
him, but will also bring into evidence the fact that his career
deserves to be better known popularly, because it illustrates very
well the typical mode of life in which great scientists are nurtured
and the methods of investigation by which great discoveries are made.
Of the men who have made the biology of the nineteenth century there
are three whose names stand out with special prominence. They are
noted not for their controversial writing on mooted points, but for
ground-breaking, original work of the highest scientific import. Their
discoveries will preserve their memories for posterity long after the
names of many of those to whom the glare of controversial publicity
lent an ephemeral brightness for their own {255} generation shall have
been forgotten. They are: Theodore Schwann, the anatomist, to whom
modern biology owes its foundation by the establishment of the cell
theory; Claude Bernard, the physiologist, to whom we are indebted for
the great biological ideas of nervous inhibition and internal
glandular secretion; finally Louis Pasteur, the
chemist-bacteriologist, to whom is due the refutation of the
annihilatory abiologic doctrine of spontaneous generation, and the
discoveries that have revolutionized modern medicine and promise to
accomplish as great a revolution in modern manufactures and
industries.
It has often been said that the Catholic Church is opposed to
scientific advance. It has especially been insisted that in what
concerns biological science the Church's attitude has been distinctly
discouraging. Recently the definite assertion has been made that no
original thinker in science could continue in his profession of faith.
Now, it so happens that all three of these men were born in the bosom
of the Catholic Church, and were educated from their earliest years to
maturity under her watchful care. Schwann and Pasteur remained in the
midst of their great scientific triumphs her faithful sons. For years
Bernard withdrew from all his old religious associations and became
indifferent to the spiritual side of life, but before the end he came
back to the knees of the Mother whose fostering care meant so much to
him in early life.
Theodore Schwann, the first to formulate the cell doctrine, to
promulgate the teaching that all living tissues, whether plant or
animal, are composed of a number of minute elements which under all
circumstances are biologically equivalent--is the father of modern
biology. Cells had been seen and recognized as such before, but their
significance was first pointed out by him. His cell theory has now
become the {256} cell doctrine, the teaching of all the schools of
biology. The generalization that forms the basis of the doctrine was
the result of some of the most accurate and careful observation that
has ever been made. The work was done when the mechanical helps to the
analysis of tissues were in the most primitive condition. The
microscope had just been introduced into general laboratory work. The
microtome, the instrument by which tissues are cut into thin sections
suitable for microscopic examination, and to which almost more than to
the microscope itself we owe our detailed knowledge of the intimate
constitution of tissues, was as yet unthought of. Despite these
drawbacks Schwann's work was done with a completeness that leaves very
little to be desired. He published, when not yet thirty, the story of
his comparative investigation of the cellular constitution of plants
and animals, and there is very little that can be added, even in our
day, to make its scientific demonstration any clearer than it was. It
was typical of the man that, heedless of disputatious controversy over
details of his work, he should go calmly on to complete it, and then
give it to the world in all its convincing fulness. The same trait
crops out with regard to other subjects. His was one of the great
scientific minds of the century, always immersed in a philosophic calm
befitting the important problems he had in hand. His life is ideal in
its utter devotion to science, and to the teaching of science, while
no duty that could round it out and make it humanly complete for
himself or others was despised or neglected.
Theodore Schwann was the fourth of a family of thirteen children, born
in the little German town of Reuss, not far from Cologne. He received
his college education in the Jesuit Gymnasium of Cologne, and passed
thence to the University of Bonn. The lower Rhineland is largely {257}
Catholic, and to this day, though Bonn has become the fashionable
exclusive German university to which the Kaiser and many of the scions
of the great German families go for their higher education, the
faculty of theology at the university remains Catholic. Schwann
devoted some time here to the study of theology, but he came under the
influence of Johann Mueller, was allowed to assist in some of his
experiments on the functions of the spinal nerves of frogs, and this
seems to have determined him to a medical career.
After two years spent in medicine at Wuerzburg, another great Catholic
university of Southern Germany, we find Schwann at the University of
Berlin, once more working with Johann Mueller, who had been invited
from Bonn to fill the distinguished Rudolphi's place in the chair of
anatomy at the rising Prussian university. Mueller was one of those
wonderful men--they turn up, unfortunately, all too rarely--who,
though not great discoverers themselves, have the invaluable faculty
of inspiring students with an enthusiasm for original observation
which leads to the most brilliantly successful researches. A great
teacher, in the proper sense of the word, he was not. In his public
lectures and his ordinary lessons he was often arid and uninteresting,
insisting too much on unrelieved details, "the dry bones of science."
He seems to have failed almost completely in conveying the usual
scientific information of his course with the air of novelty that
attracts the average student. The true teaching faculties are not
given to many. Mueller had a precious quality all his own that has
proved much more valuable for science than the most enlightened
pedagogy.
To the chosen few among his students who were drawn into close
intimacy with him and permitted to share his personal scientific
labors, Mueller proved a source of most precious incentive--a
suggestive master, the inspiration of {258} whose investigating spirit
was to be with them throughout life. To no one, except perhaps to
Socrates of yore, has it been given to have sit at his feet as pupils
so many men who were to leave their marks upon the developing thought
of a great era in human progress. Beside Schwann, there studied with
Mueller, during these years at Berlin, Henle the anatomist, Bruecke the
physiologist, Virchow the pathologist, Helmholtz the physicist, Du
Bois-Reymond the physiologist, Claparede, Reichert, Lachmann,
Troschel, Lieberkuehn and Remak. All these names are writ large in the
scientific history of the century. It is a remarkable group of men,
and of them Schwann, with the possible exception of Helmholtz, will be
remembered the best by posterity; certainly none of them would not
have cheerfully resigned his hopes of scientific renown for any work
of his own to have made the discovery which, as an enthusiastic
biographer said, set the crown of immortality on a young, unwrinkled
forehead.
Schwann's thesis for his doctorate at Berlin showed the calibre of the
man, and demonstrated his thorough fitness for success as an
experimental scientist. The question whether the growing embryo in the
ordinary hen's egg consumes oxygen or not had been in dispute for some
time. It was well known that an air-chamber existed in the egg even at
the earliest stages of embryonic life. It was understood that the
mature chick just before its egress from the egg must have air, and
the porosity of the egg-shell was sufficient to permit its entrance.
Whether at the beginning of embryonic life within the egg, however,
oxygen was necessary, remained somewhat in doubt. It had been
demonstrated that the gas existing in the air-chamber of an egg became
changed in composition during the progress of development. From being
slightly richer in oxygen than ordinary atmospheric air at the
beginning of embryonic growth, {259} containing 24 to 25 parts of
oxygen per 100, it became modified during comparatively early
development so as to contain not more than 17 parts of oxygen per 100
and some 7 parts of carbon dioxide. This change of composition was, at
least, very suggestive of the alteration that would take place during
respiration. It was pointed out, however, that the argument founded on
these observations was drawn only from analogy, and was by no means a
scientific demonstration of the fact that the embryo not only consumed
air during its growth, but actually needed oxygen for the continuance
of its vital processes.
It was suggested that the change of composition in the air within the
egg might be due not to any essential vital functions, but to chance
alterations brought on by decomposition in the unstable organic
material so abundantly present in the substance of the egg. Schwann
settled the question definitely by a set of ingenious experiments. He
exposed eggs for various periods to the action of other gases besides
air, and also placed them in the vacuum chamber of an air-pump. When
not in contact with the air the eggs developed for some hours if the
temperature was favorable, and then development ceased. If after
twenty-four hours' exposure to an atmosphere of hydrogen eggs were
allowed free contact with the air, development began once more at the
point at which it had ceased. After thirty hours of exposure to
hydrogen, however, or to the vacuum, all life in the egg was
destroyed, and it failed to develop no matter how favorable the
conditions in which it was afterward placed. The completeness with
which the points in dispute in this problem were demonstrated is
typical of all Schwann's work. His conclusions always went farther
than the solution of the problem he set out to solve, and were always
supported by simple but effective experiments, often ingeniously
planned, {260} always carried out with a mechanical completeness that
made them strikingly demonstrative.
One of Schwann's brothers had been a worker in metal, and Schwann
himself had always shown a great interest in mechanical appliances.
This hobby stood him in good stead in those days when laboratories did
not contain all the intricate scientific apparatus and the facilities
for experimentation so common now, with their workshop and skilled
mechanics for the execution of designs. Many another worker in the
biological sciences of that time owes his reputation to a similar
mechanical skill. Experiments were impossible unless the investigator
had the mechanical ingenuity to plan and the personal handiness to
work out the details of appliances that might be necessary for
experiments. It is told of Schwann that when Daguerre's discoveries in
photography were announced, such was his interest in the new invention
that he made a trip to Paris especially to learn the details of the
method. Some daguerreotypes made by him according to the original
directions of the inventor himself are still preserved by his family.
Schwann's investigation of the respiration of the embryo in hens' eggs
led to further studies of the embryo itself, and to the discovery that
it was made up of cells. Later came the resolution of other tissues
into cells. When, after his graduation as doctor in medicine, the post
of assistant in anatomy at Berlin fell vacant, it was offered by
Johann Mueller to Schwann. The position did not carry much emolument
with it. The salary was ten German thalers--_i.e._, about $7.50 per
month--a pittance even in those days when the purchasing power of
money was ever so much greater than now. His duties took up most of
his time. The work was congenial, however, and Schwann remained here
for five years. As Henle has said in his biographical sketch of {261}
Schwann, in the _Archiv f. mikroskopische Anatomie_, just after his
death in 1882: "Those were great days. The microscope had just been
brought to such a state of perfection that it was available for
accurate scientific observations. The mechanics of its manufacture had
besides just been simplified to such a degree that its cost was not
beyond the means of the enthusiastic student even of limited means.
Any day a bit of animal tissue, shaved off with a scalpel or picked to
pieces with a pair of needles or the finger-nails, might lead to
important ground-breaking discoveries." For at that time almost
everything as to the intimate composition of tissues was unknown.
Discoveries were lying around loose, so to speak, waiting to be made.
Schwann was not idle. The precious years at Berlin saw the discovery
that many other tissues were composed of cells. The nuclei of the
striped and unstriped muscles were found, and while the cellular
character of these tissues was not demonstrated, their secret was more
than suspected and hints provided for other workers that led very
shortly to Koelliker's and Henle's discovery of muscle cells.
Besides his interest in histology, the branch of anatomy which treats
of the intimate constitution of tissues, Schwann was working also at
certain general biological questions, and at some knotty problems of
physiology. Not long after his installation as an assistant at Berlin,
from observations on fermenting and decomposing organic liquids, he
came to a conclusion that was far in advance of the science of his
day. He announced definitely _infusoria non oriuntur generatione
aequivoca_--the infusoria do not originate by spontaneous generation.
Under the term infusoria, at that time, were included all the minute
organisms; so that Schwann's announcement was a definite rejection of
the doctrine of spontaneous generation over thirty years before
Pasteur's demonstrations finally settled the question. Schwann was
never a {262} controversialist. He took no part in the sometimes
bitter discussions that took place on the subject, but having stated
his views and the observations that had led up to them he did not ask
for the immediate acceptance of his conclusions. He continued his work
on other subjects, confident that truth would prevail in the end. When
the congratulations poured in on Pasteur for having utterly subverted
the doctrine of spontaneous generation, the great French scientist
generously referred the pioneer work on this subject to Schwann, and
sent felicitations to that effect when Schwann was celebrating the
jubilee anniversary of his professoriate.
While studying ferments and fermentations Schwann became interested in
certain functions of the human body that carry with them many
reminders of the biological processes which are at work in producing
the various alcohols and acids of fermentation. The changes that occur
in the contents of the human stomach during the preparation of food
for absorption had long been a subject of the greatest interest to
physiologists. It had been studied too much, however, from the merely
chemical side. The necessity for the presence of an acid in the
stomach contents in order that digestion should go on led to the
conclusion that the acid was the most important constituent of the
gastric juice. By means of the scrapings of the stomachs of various
animals Schwann succeeded in preparing an artificial gastric juice,
and showed just how the action of the gastric secretions brought about
the solution of the contents of the stomach. He isolated pepsin, and
demonstrated that it resembled very closely in its action the
substances known as ferments. He even hinted that digestion, instead
of being a chemical was a biological process. Any such explanation as
this was scouted by the chemists of the day, headed by Liebig. Most of
the physiological functions within the human body were {263} then
triumphantly claimed as examples of the working of chemical laws.
Of the contradiction of his conclusions Schwann took practically no
notice, but went faithfully on with his work. He could not be lured
into controversy. For nearly five years he continued his work at the
University of Berlin, receiving only the pittance that has been
mentioned--less than ten dollars per month. Only the purest love of
science for its own sake, and the satisfaction of his own enthusiastic
spirit of investigation kept him at work. There was but little
prospect of advancement at the University of Berlin itself. Schwann
was one of the lowest in rank of the assistants; the professor was
only just beyond the prime of life; and before Schwann on the list for
promotion was at least one man, Henle, who had already done
distinguished work. Germany had the good fortune to have all during
the nineteenth century young men who, unmindful of present emolument,
had been satisfied with the scantest wages for their support, provided
the positions they occupied gave them opportunities for original work.
Even at the present day young medical men are glad to accept what they
consider the honor of the position of assistant to the professor and
director of the clinic, and to remain in it for from five to ten
years, sometimes even more, though the salary attached to it is only
from $250 to $400 per year. They well know that if their original
investigations into various medical questions are successful, advance
in university rank is assured. Their promotion seldom comes from the
institution where they have done their work, unless it should be one
of the smaller universities; but the invitation to a chair at a
university will come sooner or later for meritorious research.
Schwann's invitation came from Louvain. His work on cells had
attracted a great deal of attention. In the midst {264} of the
rationalism and infidelity then so common among scientific men Schwann
was known as a faithful, sincere Catholic. When the great Catholic
University of Louvain, then, looked around for a professor of anatomy,
he appeared to be the most suitable person. Henle, who had very little
sympathy for Schwann's religious views, speaks most kindly of him as a
man and a comrade. Schwann seems to have endeared himself to the
"difficult" Prussians, as he did to those around him all his life. For
the dominant note in the sketches of him by those who knew him
personally is that of heartiest friendship, joined with enthusiastic
admiration for his simple sincerity and unselfish devotion to his
friends and to science.
A little incident that has been preserved for us by Henle shows how
much his young contemporaries appreciated even at that early date,
long before the full significance of the cell theory could be
realized, the aspect of Schwann's work which was to make him immortal.
At a little farewell dinner given him by his co-workers in various
laboratories of the University of Berlin the feature of the occasion
was a punning poem, by the toast-master, on the words Louvain and
cells.
In German Louvain is Loewen, which also means lion; that is, it is the
dative case of the name of the lion. Reference is made to the fact
that as Samson found honeycomb (in German, bee-cells) in the lion, so
now Louvain--_i.e._, in German, Loewen, the lion--finds a champion in
the man of the cells. As Samson's riddle was suggested by finding the
bee-cells, so will the new professor at Louvain solve the riddles of
science by the demonstration of cells. The youthful jesting seer
prophesied better than he knew. Schwann's first completed work at
Louvain was the _Microscopical Researches into the Accordance in
Structure and Growth of Plants and Animals._ [Footnote 11] {265} The
theory it advanced was to prove the most potent element thus far
introduced into biological science to help in the solution of the
difficult problems that constantly occur in the study of the various
forms of life.
[Footnote 11: Mikroskopische Untersuchung ueber die Uebereinstimmung
in der Structur und dem Wachsthum der Thiere und Pflanzen, 1839.]
At Louvain, Schwann remained for about ten years. The period is marked
by a continuance of his fruitful investigation of cell-life, of the
physiological biology of ferments and fermentation, and of the allied
subject of digestion in animals. His researches in Berlin on this
interesting and important subject, which was practically a complete
mystery at that time, had been mainly concerned with the gastric
juice. He now began the study of various secretions which aid
intestinal digestion. He proved that bile, which used to be considered
an excretion, was really an important digestive secretion. He was not
able to demonstrate the function of bile as completely as he had done
for the gastric juice. The problem of intestinal digestion is much
more complicated than that of stomach digestion, and involves a number
of factors for which allowance has to be made if the value of any one
of them is to be accurately determined. Even in our own day all of the
physiological problems in the functions of biliary secretion are not
solved. The greatest step was the demonstration that bile is a thing
whose presence in the intestines is to be encouraged, not because, as
Horace said, mental trouble was imminent unless one were purged of
black bile in the springtime, but because its presence insures the
proper preparation of food, and neutralizes in the intestinal tract
certain poisonous substances that if absorbed would prove sources of
irritation to all higher tissues.
His work on bile practically closes Schwann's career as an
investigator. The seven years between twenty and {266} twenty-seven
were so full of discovery that there seemed to be great promise for
his mature years. Had Schwann died at thirty his biographies would
have surely contained lengthy comments on the great discoveries that
would undoubtedly have rewarded his efforts in the prime of his
powers. Schwann's seeming inactivity has been a fruitful cause for
conjecture. The fact of the matter is, however, that original work of
a high order is accomplished mainly during the time when activity of
the imagination is at its height. There are very few cases in which
this acme of inventive effort has lasted more than ten years.
Besides this there were certain more material factors that hindered
original work. Schwann was a German, yet had to give his lectures at
Louvain in French. For several years most of his efforts were devoted
to acquiring facility in the language of his adopted country. Then
Schwann was not such a teacher as Mueller, but the true pedagogue who
took seriously to heart the duty of teaching all his students. To do
this meant, in the rapidly advancing science of that day, unceasing
toil on the part of a conscientious professor. For it was a time of
great discoveries succeeding one another with almost incredible
rapidity. For ten years Schwann faithfully devoted himself to his
teaching duties in the anatomical course at Louvain. He then accepted
the chair of comparative anatomy and physiology at Liege, where he
continued to lecture for thirty years. As the result of his stay at
Louvain there has always been special attention given to biological
studies at that university. At the present time there is published
there a very well and favorably known biological journal, _La
Cellule_, through which many important contributions from the
professors and students of the university find their way before the
public.
During his stay at Liege Schwann was formally invited, {267} on three
different occasions, to return to his German Father-land to become
professor at some of her great universities. Professorial chairs in
anatomy or physiology at Wuerzburg, at Giessen, and at Breslau, were
offered him between 1850 and 1860. He refused them, however, to
continue his work in Belgium. He found his adopted countrymen
eminently sympathetic. It seems clear that he felt more at home in the
midst of the profoundly Catholic sentiment that pervaded the Belgian
universities, and which was in such marked contrast to the
rationalistic spirit characteristic of the German universities at that
time. Schwann was penetrated with a lively sense of the deepest
religious feeling, which is noticeable all through his life. His
attitude in this matter greatly impressed his scientific
contemporaries. His sense of duty in matters spiritual was only
equalled by his affectionate regard for his relatives. His vacations
were invariably spent with his parents while they were alive, and
later with his brothers and sisters in the neighborhood of Cologne. It
was while making a Christmas visit to them that he suffered the fatal
stroke which carried him away.
Toward the end of his career Schwann was invited to be a member of a
commission to investigate the case of Louise Lateau. It will be
remembered that the report of recurring bleedings from stigmata in
this case attracted a great deal of attention, not only among
Catholics, but among all classes throughout the world. After careful
observation Schwann refused to concur in the report that the bleedings
were manifestly miraculous. At first it was announced that he had
declared them evidently beyond the domain of natural causes, but this
report he took occasion to correct immediately. The circumstance led
to the publication of some harsh words in the religious press, but
with his usual moderation Schwann refused to enter into any
discussion, and so the affair ended. {268} His thoroughly conservative
attitude in the matter, and his application of the strictest
scientific criteria to the case, prevented formal expression of
approval on the part of those in authority. While such an opinion
would have carried only personal weight with it, it might easily have
been made a cause for unfortunate aspersions upon the Church.
The most marked feature of Schwann's career is the unfailing
friendships that linked him to those with whom he was associated. At
Louvain, and later at Liege, he was the personal friend of most of his
students, while at Berlin he made friendships with some of the great
men in German medicine which endured to the end of his life. When the
celebration of his fortieth anniversary came around, the hearty
tributes from all over Europe showed in what lofty reverence the
kindly old man was held, who had sacrificed some of his chances for
greater scientific fame in order to be a teacher of others, and a
living exponent of the fact that the frame of mind which leads to
great scientific discovery and that which bows humbly to religious
truth, far from being hopelessly and essentially opposed to each
other, may be peacefully united in the same person in their highest
expression.
{269}