Chapter IX: Preface (8)

His habits of experimentation on one occasion at least placed him in a rather ridiculous position. While making his military service, it happened one day that when the command "Order arms" was given, Mueller amused himself by inserting one finger after another into the muzzle of his firelock. At last his middle finger got fairly wedged into the weapon. When the order attention was given, Mueller could not withdraw his finger. His predicament at once attracted notice, and he was ordered to the front to be reprimanded by the major, to the no small amusement of his comrades, who laughed heartily at his ridiculous predicament. He was sent to his quarters in disgrace and the regimental surgeon had no little trouble in liberating the thickly swollen finger.

While everything thus seemed to promise a life of experimentation, Mueller's imagination had a powerful hold on him, and he gave himself up for some time to certain mystical theoretical questions and problems of introspection which, for a time, threatened to take him away from his real calling of an experimental physiologist. Fortunately for Mueller, as we shall see, though at the moment he doubtless {230} thought it a serious misfortune, these excursions into a too introspective psychology were followed by nervous troubles, what we could now call neurasthenia, and he was consequently led back to the study of external nature.

Just after Mueller's promotion to the doctorate in medicine, the Rhenish universities came once more under the authority of the Prussian government, and Berlin became a Mecca for students, who looked upon it in a way as the mother university. After his graduation at Bonn, then, Mueller was attracted to Berlin, and came especially under the influence of Rudolphi, who recognized his talents and gave him special opportunities for original investigation. Rudolphi's private library and his collection were placed at the command of this young original worker, who had already proved his power of investigation and his capacity for following a subject to its ultimate conclusions, even though those were not yet extrinsically known. While at Berlin, too, Mueller came under the influence of the younger Meckel, whom he learned to respect very much. After Meckel's death the _Archives of Physiology_, previously edited by Meckel, fell into Mueller's hands, who successfully continued it for many years.

At Mueller's departure from Berlin he was presented by Rudolphi with an English microscope, as a testimonial of the old professor's appreciation of the young man's labors while under his observation. As Mueller's pecuniary resources were very limited, this must have been an especially acceptable gift, since it enabled him to continue his researches in embryology, and it was not long before these began to bear fruit. At Bonn, to which Mueller returned, he set up as a Privat-Docent in the University, and for several years eked out by teaching the allowance his mother could give him, and even by the practice of medicine.

Bonn, at this time, had a population of perhaps 30,000, {231} and had some eighteen regular practitioners of medicine. It is easy to understand, then, that Mueller's practice did not add materially to his pecuniary resources. It was not long before he gave up the practice of medicine entirely, led to the step by the sad death of a friend, who, while under his care, suffered from perforation of the intestines, followed by peritonitis. Notwithstanding the rather precarious state of his finances, at the age of twenty-six, Mueller married Anna Zeiler, the daughter of a landholder in the Rhineland, not far from Bonn. He had previously dedicated to her a poem, in which he promised her, in lieu of more material advantages as a marriage settlement, an immortal name. The young man seems to have felt something of the genius that was in him, but, then, so have others, and their presages have not always been confirmed by the issue. Shortly before and after his marriage, he applied himself so hard to his investigations of many kinds that within a few months he broke down. The government allowed him a furlough, and for several months he wandered with his bride along the Rhine, in what has been described by a biographer as a "one-horse shay," and came back to his work renewed in mind and body.

As a matter of fact, Mueller's breakdown was what would be called at the present time a neurasthenic attack, induced by overwork and too great introspection. He had been experimenting upon himself in many apparently harmless ways, but by methods which often cause serious trouble. It was not an unusual thing for him to fast, in order to note the physiological effect on his mind and senses of the absence of proper nutrition. He would often lie awake for hours at night in the darkness, experimenting upon himself and noting the phenomena induced, especially in his sight, by the total absence of light. He devoted himself, too, to the investigation of the curiosities of second sight; those interesting {232} reminders of things seen long ago, though without producing much impression, and which recur at unexpected moments, to make us think that we are seeing again when we are really only unconsciously remembering. He used to exercise a good deal the faculty of bringing up objects into his vision with all the physical peculiarities of actual sight. In this his master was Goethe, who had written extensively on this subject in treating of the phenomena of vision, and who was able himself to recall to his imagination with great vividness the many shades of colors of objects with the sensory satisfaction of actual vision. Mueller had this imaginative power only for the reds.

It is not surprising that a young man, engaged too exclusively at this sort of investigation, should have impaired his nervous equilibrium to some degree, and made symptoms, otherwise unimportant, appear to him as the index of serious illness. For a time Mueller despaired of ever being himself again. When he had regained his health, however, he realized what had been the essential cause of his nervous condition; and so he never went back to his introspective observations, considering their results somewhat in the nature of a series of illusions.

After this, Mueller devoted himself for ten years strictly to his physiological investigations. The best knowledge of what Mueller accomplished for scientific medicine, during these early years, can be obtained from Virchow's summation of the discoveries of this period made shortly after his great teacher's death.

Virchow says:

"It was Mueller who introduced to the knowledge of physiologists and
physicians the doctrine of reflex actions, which had been already
indicated by Prochaska, and simultaneously discovered by Marshall
Hall and himself. Just before this Mueller succeeded in showing an
{233} easy mode of performing experiments on the anterior and
posterior roots of the spinal nerve in corroboration of Bell's
teaching of their diverse functions. Thus he had the privilege of
establishing for all time two of the greatest practical discoveries
of the physiology of the nervous system.

"Next to the nerves the blood became the subject of his researches
and he not only naturalized in German medicine the accurate
knowledge of the fibrin and blood-corpuscles, which Hewson had
cultivated with such fertility in English literature, but he also
managed by simple experiment to demonstrate the peculiar composition
of the vital fluid. The discernment of right methods of
investigation lay ever open to his clear and cultivated intellect,
and he knew well that there were cases in which the scalpel and
experiments could not determine a question, and where the truth was
only to be elicited by means of chemical agents and physical
instruments. It was thus he discovered the peculiar gelatinous
substance found in cartilage, called chondrin; thus he proved the
existence of lymphatic hearts in the amphibia, and thus that he
determined not only the organs but all the laws which are concerned
in the production of the human voice.

"The special researches of the Bonn epoch are those of the minute
structure and anatomy of the glands. They put an end to the
controversy which had existed so long between adherents of Malpighi
and Ruysch, concerning the sacculated extremities of the glandular
follicles, and obtained for us a correct knowledge of these
important organs throughout the whole animal kingdom. Perhaps his
most important work is that of the Ducts of Mueller, the structures
(named after him) which form so important a part of the
genito-urinary system in the embryo."

Practically all this had been accomplished before he was {234} quite thirty-two years of age. In the autumn of 1832, Rudolphi, the professor of physiology at Berlin, died. As Virchow says, candidates sprung up on every side, and some who were the least qualified considered themselves best fitted for the position. Mueller took an unusual step which illustrated his decision in character, though in any other it would have seemed an evidence of conceit. He declared, in an open letter, laid before the Minister of Prussia, that his claims were superior to those of any other living physiologist, except John Frederick Meckel. So powerful was the impression produced upon the minister by this letter that he immediately appointed Mueller to the vacant chair.

Not long after his appointment to the chair of physiology at the University of Berlin Mueller completed the well-known "Hand-book of Physiology," which established his reputation. The book is sometimes spoken of as an experimental physiology, but this is not correct. Mueller was no more a mere experimentalist than Haller, and he, himself, heartily detested the tendency which experimental physiology had assumed in France, especially under the influence of Magendie. Part of Mueller's aversion to experimental physiology was aesthetic. He could not bear the idea of inflicting so much pain as many of his colleagues inflicted without a thought. In his panegyric of Rudolphi, Mueller says: "Rudolphi looked upon physiological experiments as having no relation to anatomical accuracy, and it is no wonder that this admirable man, who had at every opportunity expressed his abhorrence of vivisection, took up a hostile position against all hypotheses and conclusions insufficiently established upon physiological experiments." Mueller adds: "We could not have failed to share his righteous indignation, had we seen how many physiologists were using every effort to reduce physiology to an experimental science by the live dissection and agonies {235} of innumerable animals, undertaken without any definite plan, and yielding often only insignificant and imperfect results."

Mueller shared these views of Rudolphi with regard to vivisection. The uncertainty of the conclusions, the amount of suffering inflicted, and the indefiniteness of the conditions of experiment, so that the conclusions could not have any very great weight, or any special accuracy of information, made him consider such experiments, unless very carefully conducted by trained investigators, as largely a waste of time and infliction of unnecessary pain and a leading astray of physiological advance because of the uncertainty involved.

The qualities in Mueller's "Hand-book of Physiology," which gave it its greatest value, are the thorough review of all of the physiological literature of the world which it contains, and the greatest number of original observations it details as the basis of the principles enunciated. Mueller himself said, in the preface to his "Hand-book": "I need scarcely remark that it is the duty of a scholar to make himself acquainted with the progress of science among all nations; and this is now possible and, moreover, quite indispensable in these days of progress. A purely German, French, or English school of medical science is barbarism; and in Germany we would consider the idea of an isolated English or French system of natural history, physiology or medicine just as barbarous as the notion of Prussian, Bavarian, or Austrian medicine or physiology."

How valuable the book was as the corner-stone of modern German medicine, may best be judged from Virchow's opinion of it. He says in his panegyric of Mueller:

"There are two qualities in his 'Hand-book of Physiology' which have
particularly enhanced my estimation of its value--its strictly
philosophical method and its completeness {236} in facts. Since the
time of Haller no one has so thoroughly mastered the entire
literature of natural history or collected in all directions so many
original experiences, and no one has been at the same time familiar
with medical practice, as well as with the remotest provinces of
zoology. It has been well said that while Haller often, in doubtful
questions, espoused a side which must eventually be forced to
succumb, Mueller always had the luck (if we may call that luck which
was preceded by so much intelligent activity), sooner or later, to
discern the opinion that was sure, eventually, of the victory. He
was wonderfully fitted for the office of critic by his comprehensive
knowledge. He knew how to discriminate the healthy from the unsound,
the essential or real from the adventitious or accidental. And, in
surveying the whole series of forms--often widely different--among
which a well-determined plan of nature seemed to be realized, he
knew the changes which not infrequently altered considerably the
arrangement and composition of the substances within these forms. In
Mueller, as a physiologist, it is not the genius of the discoverer,
nor the ground-breaking nature of his observations we admire, but
rather the methodical exactness of investigation in calculating
judgment, the confident tranquility and the perfect consummation of
his knowledge."

In a word, Mueller owed the success of his career to the perfect poise of his intellect and the admirable critical faculty that guided him in the thorny path of knowledge at a time when there were so few landmarks of real scientific significance to show the investigator what the probable course and progress of real science must be. It was for this reason that, as Virchow has said, the reform of newer views became embodied in him, and in spite of the almost monastical retirement of the scholar, the influence of the method introduced by Mueller was not limited to physiology, but continues to {237} spread beyond that science in ever-widening circles into the domain of all the biological sciences.

Virchow concludes: "Mueller vanquished mysticism and phantasms in the organic kingdom and he was most distinctly opposed to every dangerous tendency, whether it was pursued under the pretext of physiology or belief, or merely in accordance with conjectures. Mueller did not discover, but he firmly established the exact method of investigating natural sciences: Hence, he did not found a school in the sense of dogmas--for he taught none, but only in the sense of methods. The school of natural science which Mueller created knew no community of doctrine, but only of facts and still more of methods."

He did not confine himself in his studies, however, to the physiology and pathology, nor even to the anatomy and embryology of man. After 1840 he devoted himself to the study of invertebrates and investigated the starfish and the pentacrinites. While engaged in his work on the invertebrates he found that the fossil remains of animals had not been carefully explored, so for a time he devoted himself to paleontology. While his salary as professor was ample for his own support, it was not what would be called generous at the present time, yet Mueller became so devoted to his science that he paid certain of the workmen to be on the lookout for fossil remains for him in the quarries of the Eifel. He became deeply interested, too, in life in the sea and made his vacations times of specially hard work, investigating the conditions of low life among marine organisms. He passed from one class of life to another. From sea-urchins and starfish to infusoria and polycystina, whose varieties he was himself the first to recognize and describe.

Mueller was one of the first to point out that certain of the lower animals could propagate similar and dissimilar {238} generations, that is, reproduce by alternate generations. He studied and demonstrated especially the metamorphoses in the echinodermata, and his broad vision and careful observation in this new and surprising scientific field cleared up many things that had been mysteries before.

In paleontology Mueller worked with our own Agassiz, then a young man, or perhaps it should rather be said that Agassiz worked with Mueller. A paper, for whose compilation they made a series of observations together, appeared at Neufchatel, in 1834. It was a note on the vertebrae of living and fossil dog fishes. At this time Mueller was interested in fossil fishes of many kinds and wrote several articles in later years on this subject. Toward the end of Mueller's life he studied especially the polycystina, certain of the radiolaria, and some of the many chambered specimens, fossil and living, that were attracting much attention at that time. As a matter of fact he went the day before his death to the zoological museum of Professor Peters in Berlin, in order to obtain some polythalamacea.

How open to advance in science and how ready to encourage the work of others Mueller was, may be gathered from his attitude to parasites as the cause of disease, when these began to be discovered. After Professor Schoenlien's discovery of the parasite of favus, Mueller became interested in it, confirmed Schoenlein's observations and added something to our knowledge of it. About this time, also, he discovered the psorosperm as a parasite of animals and possibly of man, and devoted considerable attention to it. His work was afterward greatly extended by one of his pupils, Lieberkuehn, whose researches with regard to these minute organisms attracted the attention of the medical world.

It is not a little surprising how many of the investigations that afterward were to give fame to Virchow were initiated {239} by his great teacher, Mueller. It was Mueller whose study of tumors led Virchow to devote himself to this subject and give us the best pathological work on it that has ever been written. Virchow himself notes with regret that Mueller turned aside from pathology and never finished the promised work which was to have contained his theory of the origin of tumors. Another work in which Virchow followed in Mueller's footsteps was the development of craniometry and, in general, the scientific investigations of skulls. Mueller had interested himself very much in microcephalic skulls and Virchow assisted him in the investigations of them. Many years afterward Virchow established the science of craniology in the department of anthropology, and succeeded in throwing not a little light on the origins of races by his discoveries in this matter.

After Schoenlien's discovery of the parasite of favus, Mueller became interested in the parasitology of human beings, and with Retzius, the famous Swedish anatomist, investigated certain molds which occur in the respiratory passages of birds. They succeeded in demonstrating that these vegetable parasitic growths were a form of Aspergillus. Their studies in the white owl particularly called general attention to the possibility of such molds occurring as parasites of animals. Later on, Virchow showed that these same molds occur occasionally in the respiratory passages of men. Virchow found them in three bodies at autopsy, all of them being run down individuals, two of them old subjects, and all sufferers from chronic bronchitis. Usually, when the parasites were found, there was a distinct tendency to very low resistive vitality in the tissues, sometimes proceeding even to the extent of beginning pulmonary gangrene. In reviewing the subject Virchow [Footnote 7] said that the light thrown {240} upon it by the investigations of Mueller and Retzius was of the greatest possible assistance in enabling him to identify the parasite when he found it in human subjects.

[Footnote 7: Virchow's Archiv, Bd. ix.]

The number of positive facts which Mueller brought to light in the most diverse departments of science is almost beyond calculation, and yet it is astonishing how seldom the slightest error, or even an incomplete observation, can be found in his work. On the other hand, it has happened, over and over again, that when the correctness of his observations in the beginning seemed according to other investigators to be dubious, they have come eventually to be acknowledged as representing the truth. As a rule, he went over every set of observations three times. During the second series he wrote about them. He always repeated the experiments on which his observations were founded while his material was going through the press. His manuscripts were a mass of corrections; notwithstanding this, his proof sheets were the despair of the printers.

Mueller accomplished all this only by the most careful husbanding of his time. He knew how to make use even of the ends of hours and brief intervals which others waste without a thought about them. He used to call these periods of short duration between the duties "the gold-dust of time," and said that he did not wish to lose a particle of it. In the quarter of an hour between two lectures it was not an unusual thing to find that he took up some dissection at which he was engaged, or continued his work sketching the observations that he had been making during the previous day.

How thorough was Mueller's work in everything that he devoted himself to can be gathered from certain excursions into pathology, which was, after all, only a side issue in his work, and to which he gave very little serious attention. Mueller's assistant in the Museum of Berlin, and one of his {241} favorite pupils, Schwann, made a series of what Virchow calls comprehensive and magnificent investigations on the cell structures of the animal tissues, on which progress in pathology so essentially depends. Mueller followed up these discoveries, and, to quote Virchow once more, he was in this matter the authority of authorities; for the medical world owes to him practically all its knowledge of tumors. Mueller first demonstrated the harmony which existed between the pathological and the embryonic development of tumors.

This physiological observation is of the highest importance. It came at a time when tumors were considered to have nothing of the physiological about them, but to be entirely manifestations of morbid processes foreign to all natural functions of the body. Mueller's observation of the identity of the pathological and the embryonic development of tumors is really the key to the whole doctrine of morbid formations. Virchow assures us that Mueller's labors gave the strongest impulse to the employment of the microscope in pathological investigations. Undoubtedly this was his most important contribution to scientific medicine. With this he laid the foundation of the explanations of tumors--a work that his great pupil was destined to carry on. Some of Mueller's work in this line, his study of enchondromata for instance, Virchow confesses to have been part of the inspiration that led to his own later work. Mueller was occupied, however, with too many things to devote himself to the study of pathology in the way that would have been necessary to make great discoveries in the science. He promised that he would sometime settle down to make a classification of tumors, and that the principle of such a classification would not be based either on their fineness of structure or on their chemical composition, but that their physiological nature and tendency to grow must be taken into account. When he died, however, he {242} left behind him nothing unfinished except the long-expected conclusion of his book on tumors.

Mueller's most important work in physiology, and his most far-reaching influence on the biological sciences, which were just then beginning their modern development, came from his assertion of vital force as a thing entirely different from and absolutely independent of the physical or chemical forces which it directs and makes use of. Vital force for Mueller was the ultimate cause and supreme ruler of vital phenomena, so that all the energies of an organism follow a definite plan. It was for him the complete explanation of all the physical manifestations of life. It disappears in death without producing any corresponding effect. Without losing anything of itself it hands over in multiplication or reproduction a force equal to itself to the new being that is born from it. This vital force that is thus handed over need not necessarily manifest itself at once, but may lie dormant for a long time to be awakened to manifestations of life by the concurrence of proper conditions in its environment.

In a word, Mueller appreciated fully the mystery of life, faced the problem of it directly, stated it in unequivocal terms, and by so doing saved the rising science of biology from wandering off into speculations which were seductive enough at that time, but which would have proved vain and wasteful of time and investigative energy. Mueller's influence on his students was sufficient in this matter to set the seal of vitalism, as it is called, on most of the biological work done in Germany about the middle of the century, and it was a recurrence to his observations and his methods which led the reaction to vitalistic theories that characterized the concluding years of the nineteenth century.

With regard to the significance of Mueller's work, Professor Du Bois-Reymond, himself a pupil of Mueller, in his memorial {243} address delivered before the Royal Academy of Sciences of Berlin in 1859, [Footnote 8] says: "It has been objected by those who insist on the greatness of Mueller's reputation that he himself made no discovery that can be said to be of the first rank. Mueller's fame is great enough for us to allow that there is something true in this objection. He accomplished more in developing the ideas of others than in original research of his own. That he did not make any great discovery is, however, rather due to the fact that he came at a time when great discoveries were no longer lying around loose as they had been in the preceding century, waiting to be made, as it were; and what he accomplished was of more value than one or two single discoveries of primary importance. He made the original ideas of other men so clear that they were at once accepted by all the medical and scientific world. In this way he furthered the progress of medicine better than any devotion, however successful, to one single feature could possibly have accomplished.

[Footnote 8: Gedaechtnissrede auf Johannes Mueller, von Emil Du
Bois-Reymond, Berlin, Buckdruckerei der Koeniglichen Akademie der
Wissenschaften (Dummler), 1860.]

"Mueller made mistakes, but then who ever fails to make mistakes in the face of nature? As a rule, however, he hit the nail on the head. There are many suggestive thoughts from him that the investigators of later times have proved to be true. He suggested, for instance, that there must necessarily be some connection between the ganglionic bodies and the nerve stems. He suggested, also, that there must be a special nerve system for the intestinal tract. Later discoveries in physiology have established both of these thoughts and have shown that Mueller had so entered into the spirit of nature and her processes as to be able to think her thoughts. There is no doubt that there are suggestions in {244} his writings, especially those of the later years of his life, which will give a series of triumphal substantiations of the same kind."

Du Bois-Reymond's final judgment is of special interest, because it tries to point out the comparative place that will be occupied by three great men in the biological sciences of a century ago:

"Haller and Mueller must be considered as giants of earlier days,
though when future generations compare them with Cuvier they will
occupy somewhat of the position that Galileo and Newton hold in
comparison to La Place and Gauss, or Lavoisier in comparison to
Berzelius. The first of these men had the opportunity to do great
things while it was yet possible to do them, and left to their
successors only the possibility of developing their thoughts."
[Footnote 9]

[Footnote 9: Some idea of the estimation in which Mueller was held
by his contemporaries, German and foreign, may be gathered from
the number of scientific bodies of which he was a member. He was
an associate in practically every serious scientific body in
Germany. He was, besides, foreign member of the scientific
academies at Stockholm, Munich, Brussels, Amsterdam; the
scientific societies of Goettingen, London, Edinburgh, Copenhagen;
foreign honorary member of the Academy of Sciences of Vienna;
corresponding member of the Academies of St. Petersburg, Turin,
Bologna, Paris and Messina; of the Society for Science at Upsala,
of the Mecklenburg Naturalist Society of Rostock, of the
Senkenberg Institute of Frankfort-on-Main, of the Academy of
Natural Sciences of Philadelphia, of the Society of the Museum of
Natural History at Strasbourg, of the Naturalists' Association of
Dutch East India; member of the Holland Society of Sciences,
Haarlem; of the Naturalist Society of Frieburg in Breisgau, Halle,
Dantzig and Mainz; of the American Philosophical Society of
Philadelphia, of the Society of Biology of Paris; honorary member
of the Cambridge Philosophical Society, of the Natural Science
Union of Hamburg, and the Natural Science Association of the
Prussian Rheinland and Westphalia, of the American Academy of Arts
and Sciences in Boston, of the Ethnological Society of London, of
the Microscopic Association of Giessan, member of the Society for
Science and Medicine at Heidelburg, of the Naturalists' Society at
Dresden; corresponding member of the Scientific and Medical
Association of Erlangen and Moscow; member of the Academy of
Medicine of Paris; honorary member of the Academy of Medicine of
Prague and of Dorpat, of the Medico-Chirurgical Academies of Wilna
and of St. Petersburg, of the Medical Society of Guy's Hospital in
London, of the Medical Society of Edinburgh and of the Hunterian
Society of the same city, and of the Medico-Chirurgical Societies
of London and of Zurich, of the Medical Societies of Budapest, of
Lisbon, of Algiers and Constantinople; corresponding member of the
Medico-Chirurgical Academy of Turin and of the Medical Society of
Vienna.

Even this long list does not include all his various honorary and
active memberships in scientific and medical societies. He was,
besides, the laureate, that is, a prize winner, of the Medical
Faculty of the University of Bonn, of the Soemmering Prize of the
Senkenberg Institution, of the Copley Medal of the Royal Society
of London, of the Culver Prize Monthyon of the same institution,
as well as laureate of the Academy of Sciences of Vienna for
Experimental Physiology. He had been honored by the King of
Prussia by the conferment of the knighthood of the Order of the
Red Eagle, by the King of Sweden by the Royal Swedish Order of the
North Star, by the King of Bavaria by the Royal Bavarian
Maximilian Order, and by the King of Sardinia by a knighthood in
the Order of SS. Mauritius and Lazarus.]

{245}

It is as a teacher that Mueller did his best work. He was not by nature a good talker and never said much, but he was very direct; and, as he spoke from the largest possible and most progressive knowledge of the subject, his lectures were always interesting to serious students. There seems to be a more or less general agreement that for the mass of his students he was uninteresting because likely to be above their heads. For the talented members of his class, however, he was an ideal teacher--always suggestive, always to the point, and eminently complete. Du Bois-Reymond says that he never was confused, never repeated himself, and never contradicted himself.

He was able to illustrate his lectures by sketches on the board in a way that enabled students to follow every step of {246} even a complex, embryological developmental process. He could trace, step by step, with the chalk, every stage of evolution in the organism and bring it clearly before his students. To a narrow circle of the best men within his class he became a personal friend, whose inspiration led them on to the deepest original researches. Among his students were some of the men who made German medicine and German science known all over the world in the last fifty years. Chief among them may be mentioned Virchow, Helmholtz, Du Bois-Reymond, Schwann, Lieberkuhn, the discoverer of the follicles in the intestines; Max Schultze, whose work in histology and physiology are well known; Claparede, Remak, Guido, Wagener, Lachmann and Reichert.

What he demanded of his students above all was that they should learn to help themselves. He set them tasks, gave them suggestions, directed their work, corrected their errors, but he wanted them to do work for themselves. His very presence was an inspiration. Both Virchow and Du Bois-Reymond speak of the power of his eye. Du Bois-Reymond says that there was in him an almost demoniac magic, and that students looked to him as the soldiers of the first Napoleon did when the great Emperor's words were in their ears--"Soldiers, the Emperor has his eye on you." Du Bois-Reymond adds that, consciously or unconsciously, every student felt the winning influence of his great personality. With all this he knew how to unbend, especially with favorite students, and many a joke from him found its way around the laboratory even during working hours. He was not one to stand on his dignity, and Virchow tells of him that even when nearly fifty he was known to race with a student down the corridor from one class-room door to another. He took up skating at the age of forty-five, and though he had not many friends and was too entirely devoted to his work to make {247} many acquaintances, it was always a source of pleasure to young men to be allowed to associate with him, and many eagerly sought the privilege.

How impressive a figure Mueller made in his character of teacher can be gathered best, perhaps, from a note added to Virchow's panegyric during its progress through the press, in which the pupil tells his impressions of the master:

"I must confess that Mueller, in his lectures and in his manner,
reminded me of a Catholic priest, which might be accounted for by
the impressions of his early childhood. When as the dean of the
Faculty he mounted the _cathedra superior_, dressed in his official
robes, and pronounced the Latin formulary of the proclamation of the
doctors of medicine, with short, broken and contracted words; when
he began his ordinary lectures in almost murmured syllables; or,
when with religious earnestness he was discussing any of the
abstruse questions of physiology, his tone and manner, his gestures
and looks, all betrayed the traditional training of the Catholic
priest."

Virchow adds, "Mueller himself was what he styled one of his greatest predecessors--perpetually a priest of nature. The religion which he served attached his pupils to him as it were by a sacred bond; and the earnest, priest-like manner of his speech and gestures completed the feeling of veneration with which everyone regarded him."

In the recently issued life of von Helmholtz, the great German physicist, his biographer makes it very clear how much Helmholtz thought of Mueller, one of the earliest teachers. [Footnote 10] Helmholtz, Bruecke, and Du Bois-Reymond were warm personal friends (college chums we would call them in America), and all fervent admirers of their greatest {248} master, who showed them, as Helmholtz says, "how thoughts arise in the brains of independent thinkers." A half-century later, in his recollections of the time, he said: "He who has come in contact with one or more men of the first rank has his mental intellectual standard for all time broadened, and such contact is the most interesting thing that life can hold." Curiously enough, one of the most interesting things in Helmholtz's recollections is that, despite the fact that the poverty of his parents made it advisable for him to get through his medical studies as soon as possible, Mueller persuaded him to take another year's medical work before going up for his graduation. This was mainly for the purpose of having his pupil complete an essay in physiology on which he was engaged. Mueller offered him the use of his own laboratory and all his instruments for this purpose. His judgment was justified by Helmholtz's wonderful work on the conservation of energy made within a few years after his graduation.

[Footnote 10: Herman von Helmholtz, von Leo Koenigsberger. Bd. 2,
Braunschweig, Friedrich Viewig und Sohn, 1902-3]

Mueller's death was sudden, though not entirely unexpected. He had been ailing for many months and had resolved to give up his lectureship. He had made most of his preparations for settling up his affairs, and had even sent for his son, who was practising medicine at Cologne, to come up to see him. He made a special engagement for a consultation with his physician for a certain morning, and having gone to bed in reasonably good spirits, in fact, feeling better than he had for a long while, was found dead in the morning. Some time before he had made his will forbidding an autopsy, and so the exact cause of death will never be known, though it is rather easy to surmise that it was due to apoplexy, as arteriosclerosis--that is, degeneration of arteries--had been noticeable in Mueller for some years, and his temporal artery particularly had become hard and tortuous.

Mueller was buried with all the rites of the Church, and as {249} in Germany the ecclesiastical authorities are very strict in this matter, there can be no doubt that the great physiologist had been a faithful Catholic. He was known for his edifying attendance at Mass on all the Sundays of the year. Many years afterward, in the midst of the Kulturkampf in the early seventies, a monument was erected to him in his native Coblentz, and the occasion of its unveiling was taken by the Catholic Rhineland for a celebration in honor of their great scientist.

For a time, in his younger years, Mueller appears to have been not all unaffected by the materialistic tendencies so rife in the science of the time. His early anatomical investigations seem to have clouded somewhat his faith in things spiritual. One of the expressions attributed to him before his twenty-fifth year is that nothing exists in the human being which cannot be discovered by the scalpel. It was not long, however, before Mueller repudiated this expression and came back to a realization of the importance of the immaterial. Another expression attributed to him, "Nemo psychologus, nisi physiologus," "No one can be a psychologist, unless he is a physiologist," has been often repeated as if Mueller meant it in an entirely materialist sense. As a matter of fact, however, it is intended to convey only the idea that no one can really exhaust the science of psychology unless he knows the physiology of the brain, the organ which the mind uses in its functions in this life. The expression is really the foundation of the modern physiological psychology, which is by no means necessarily materialistic in its tendency, and has become a favorite subject of study even with those who appreciate thoroughly the importance of the immaterial side of psychology.

Mueller seems never to have gotten so far away from the Church as that other great physiologist of the succeeding generation in France, Claude Bernard, who for many years allowed himself to be swamped by the wave of materialism {250} so likely to seem irresistible to a scientist engaged in physiological researches. But, even Claude Bernard came back to the Church before the end, and, under the guidance of the great Dominican, Pere Didon, reached the realization that the only peace in the midst of the mysterious problem of life and the question of a hereafter is to be found in a submissive faith of the doctrines of Christianity.

Many years ago, when Virchow took it upon himself to say harsh words in public of Catholic scholarship, and to put forward the hampering influence of the Church on intellectual development as a reason for not allowing Catholics to have any weight in educational matters, the organ of the Catholics of Germany, _Germania_, reminded him that his own teacher, the great Johann Mueller, the acknowledged father of modern German medicine, and the founder of the fecund scientific method to which so many discoveries in the biological and medical sciences are due, had been brought up and educated a Catholic, had lived all the years of his productive scholarship and fruitful investigation in her bosom, and had died as an acknowledged son of the great mother Church.

Mueller is certainly one of the great names of nineteenth century science. When many another that seems now as well, or perhaps even better known, shall have been lost, his will endure, for his original researches represent the primal step in the great movement that has made possible the advances in nineteenth century medicine. He was honored by his contemporaries, venerated by the men of science who succeeded him; he has been enshrined in a niche for himself by posterity, and his name will remain as that of one of the great geniuses to whose inventive faculty the world owes some of those steps across the borderland into the hitherto unknown which seem so obvious once made, yet require a master mind to make and mean so much for human progress.

{251}

THEODORE SCHWANN, FATHER OF THE CELL DOCTRINE

{252}

My message is chiefly to you, Students of Medicine, since
with the ideals entertained now your future is
indissolubly bound. The choice lies open, the paths are
plain before you. Always seek your own interests, make of
a high and sacred calling a sordid business, regard your
fellow-creatures as so many tools of trade, and, if your
heart's desire is for riches, they may be yours; but you
will have bartered away the birthright of a noble
heritage, traduced the physician's well-deserved title of
the Friend of Man, and falsified the best traditions of an
ancient and honorable Guild. On the other hand, I have
tried to indicate some of the ideals which you may
reasonably cherish. No matter though they are paradoxical
in comparison with the ordinary conditions in which you
work, they will have, if encouraged, an ennobling
influence, even if it be for you only to say with Rabbi
Ben Ezra, "What I aspired to be and was not, comforts me."
And though this course does not necessarily bring position
or renown, consistently followed it will at any rate give
to your youth an exhilarating zeal and a cheerfulness
which will enable you to surmount all obstacles--to your
maturity a serene judgment of men and things, and that
broad charity without which all else is naught--to your
old age that greatest of blessings, peace of mind, a
realization, maybe, of the prayer of Socrates for the
beauty in the inward soul and for unity of the outer and
the inner man; perhaps, of the promise of St. Bernard,
"Pax sine crimine, pax sine turbine, pax sine rixa."
--Osler, _Teacher and Student, Aequanimitas_.

{253}

THEODORE SCHWANN, FATHER OF THE CELL DOCTRINE.

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.