SCHWANN, THEODOR AMBROSE HUBERT

(b. Neuss, Germany, 7 December 1810; d. Cologne, Germany, 11 January 1882)

physiology.

An account of Schwann’s early life has some of the qualities of an edifying tale of saintly childhood. To his teachers and fellow pupils in primary school and at the progymnasium, Schwann was a cooperative child, diligent and modest. Little tempted by the delights of society, lacking self-confidence, and excessively shy, he withdrew into study, family life, and piety. Equally brilliant in all branches of learning, he showed a particular inclination for mathematics and physics. Given his lack of interest in the outside world, it was accepted that his vocation should be directed toward the Church when he left his native town in 1826 to enter the Jesuit College of the Three Crowns in Cologne.

Here Schwann came under the influence of an exceptional religious teacher, Wilhelm Smets. To Schwann, until then acquainted only with the strict aspects of piety, but also endowed with a brilliant intelligence and a lively sensibility, Smets’s teaching of religion was the revelation of an entirely new aspect of God and especially of the singular fact of the liberty of man with regard to the whole of nature. It was from him that Schwann learned the lesson of the elevation of man by personal perfection.

Increasingly enamored with reason, Schwann renounced theology to take up medical studies. His philosophical position became that of a Christian rationalist whose personal philosophy was in the tradition of Descartes and Leibniz.

In October 1829 Schwann entered the University of Bonn, where he enrolled in the premedical curriculum and obtained his bachelor’s degree in 1831. During this time, he attended Johannes Müller”s lectures on physiology and began to assist him in the laboratory. In the autumn of 1831 he moved to Würzburg, where he studied for three semesters, attending clinical lectures. In April 1833 he left Wüezburg for Berlin. Where Müller had been appointed to teach anatomy and physiology. In Berlin, Schwann attended clinical demonstrations and, under Müller’s guidance, prepared a dissertation on the necessity of air for the development of chicken eggs. He obtained the M.D. on 31 May 1834 and passed the state examination on 26 July. Schwann immediately became one of Müller’s assistants and devoted all his time and efforts to research.

Although he remained a practicing Catholic. Schwann abandoned himself, especially after the death of his mother in 1835, to an extreme mechanistic tendency, which guided him in the impressive work he accomplished at Müller’s laboratory in Berlin between 1834 and 1839. Schwann’s conception of God at this time was the philosophical and impersonal God of Descartes.

During this period, Müller’s was working on the Handbuch der Physiologie, which introduced into Germany Magendie’s experimental method in medical studies. Until his death Müller remained a convinced vitalist. Recourse to experimentation was for him (as it had been for Bichat) a means of studying the effects of the vital force peculiar to each organ. Restricted in his chemical and physical background, he progressively detached himself from physiology and devoted himself entirely to comparative morphology, in which field he acquired fame. On the other hand, from the beginning of his career as a researcher Schwann took a completely different position, which inaugurated the quantitative period of physiology.

Müller’s Handbuch was not merely a compilation; he critically examined all the notions that he printed. Repeating the experiments of others, suggesting new ones, opening avenues not yet explored, this treatise is a work as unique in its conception as in its realization. In the section entrusted to him, Schwann enriched Müller;s Handbuch with the results of extensive work and contributed numerous new notions. This book also contains an account of a study clearly showing Schwann’s innovating tendency: his first experiments can be dated, on the basis of his laboratory notebooks, at 16 April 1835. In these Schwann envisaged experiments in which it would be possible to subject the physiological properties of an organ or of a tissue to physical measurement. One such method involved measuring the secretion of a gland. But it was the muscle that seemed to him likely to furnish the most rewarding results. He planned to measure the length of a muscle contracted by the action of the same stimulus for different loads or, further, to compare the intensity of the contraction with that of the stimulus. He accomplished this experiment by means of the “muscular balance” and in a sense established the first tension-length diagram.

The influence in physiological circles of this simple experiment is difficult for us to appreciate. “It was the first time,” as du Bois-Reymond emphasized. “that someone examined an eminently vital force as a physical phenomenon and that the laws of its action were quantitatively expressed.” In a milieu where the idealistic philosophy and the theories of Fichte and Hegel were still dominant, the fundamental Versuch came as a revelation and constituted the point of departure for a new physiology. Dissociating itself from the teaching of Müller and resolutely abandoning the notion of vital force for the study of molecular mechanisms, the school stemming from Schwann’s experiment was distinguished particularly by the work of his successors at the Berlin laboratory, Emil du Bois-Reymond and Hermann von Helmholtz.

Parallel with his experiments on muscle, Schwann pursued the researches that led to his discovery of pepsin. About 1835, however, Gay-Lussac’s observations, prompted by Nicolas Appert’s experiments, made acceptable the notion that oxygen was the agent of both fermentation and putrefaction. This observation stimulated a recrudescence of the theories of spontaneous generation and a tendency to return to the ideas of Needham, for whom the effect of heat was to deprive the air of the oxygen necessary for the birth of “animalcules.”

Having observed that neither infusorians nor the smell of putrefaction appeared in a maceration of meat that had been boiled, Schwann noted the appearance of both these phenomena when he used an unboiled maceration or unheated air. Convinced that it was the destruction of germs that prevented the development of infusorians and molds, and that prevented putrefaction, Schwann wished to make a counterproof by showing that the heating of air did not prevent the operation of a chemical process to which it contributed oxygen, and not germs. He demonstrated that a frog breathes normally in previously heated air; and he investigated alcoholic fermentation, which also depended, in the current opinion, on the presence of oxygen. To his great astonishment, Schwann observed that heating the air he bubbled through a boiled suspension of yeast in a sugary solution prevented fermentation in certain experiments. In January 1836 he noted in his laboratory notebook the conclusion that alcoholic fermentation is the work of a live organism.

The description of the multiplication of yeast cells appears in Schwann’s laboratory notebook under the date 16 February 1836. The first public announcement of the relationship between alcoholic fermentation and the life cycle of yeast was by Cagniard de La Tour, who described the multiplication of yeast in the issue of L’Institut for 25 November 1836. Schwann’s paper (1837), however, independently demonstrated the living nature of the agent of fermentation and presented arguments of a new sort.

Schwann was led to the idea that alcoholic fermentation was related to the metabolism of yeast by his conception that putrefaction was related to the metabolism of live organisms. The prevailing doctrine in Müller’s laboratory was the vitalism derived from Paracelsus, and his principles were hostile to the Cartesian unity of natural antagonism toward this intellectual attitude had already been clearly manifested in his studies of muscle, of the mechanism of digestion, and of fermentation. His tendency to introduce a more exact mode of explanation than the current one in terms of the “vital force” culminated in the formulation of the cell theory.

The cell theory prolonged, on the biological terrain, the old debate over continuity and discontinuity in nature. The search for a common sructural principle of live organisms, excluding such imaginary entities as Buffon’s “molecules,” has preoccupied many scientists. In his biography of Virchow, E. H. Ackerknecht distinguished several searches for a common principle. In the eighteenth century the principle was the “fiber”. According to this view, which Ackerknecht designated as the first cell theory, the development of fibers began in little globules, like those recognized by Prochaska (1797). After these views were abandoned, a new theory appeared that John R. Baker termed “globulist,” Ackerknecht’s second cell theory. Its adherents included Lorenz Oken, Meckel, Mirbel, Dutrochet, Purkyne, Valentin, and Raspail. The notion of “globule” embraced a great variety of elementary units: The globulists often included some form of cell among their “globules”; but none of them can be regarded as having conceived of the organism as composed solely of cells, of modified cells, or of products of cells. It was not until 1830 that the perfecting of the microscope permitted Robert Brown to recognize the presence of the nucleus as the essential characteristic of the plant cell.

In 1839, in his Mikroskopische Untersuchungen, Schwann formulated what Ackerknecht called the third cell theory, which insists on the common cellular origin of every living thing. By “cell’ Schwann meant “a layer around a nucleus” that could differentiate itself: covered by a membrane, as the site of deposit of a more consistent substance; growing hollow, as a vacuole; or fusing itself with the “layer” of other cells. He also though (incorrectly) that cells form around a nucleus within a “blastema,” an amorphous substance that can be intracellular or extracellular. Ackerknecht’s fourth cell theory, which remians current, is that of Remak and Virchow, the first part of which follows Schwann in acknowledging the cellular composition of organisms, with the cell as the vital element, the bearer of all the characteristics of life. The second part of this theory, expressed in the dictum “omnis cellula e cellula,” contradicts Schwann’s erroneous belief in the formation of cells within a “blastema.”

The Mikroskopische Untersuchungen is composed of three parts. The first is devoted to a microscopic study of the chorda dorsalis in frog larvae. Studying that structure, Schwann found that it consists of polyhedral cells that have in or on the internal surface of their wall a structure corresponding to the nucleus of plant cells. New cells are formed within parent cells. He also found the structure of cartilage to be in accordance with the tissues of plants, and he believed that he had observed that the cartilage cells contain a nucleus and that they originate by formation of the nucleus, around which the cell develops. Schwann therefore was convinced that the cells of the chorda dorsalis and of cartilage were derived from structures of the same kind as the plant cells, with nucleus, membrane, and vacuole.

In the second part Schwann presented a demonstration of the same notion with regard to much more specialized elementary parts. He found that the varied forms of the “elementary parts” of tissues—be they epithelium, hoof, feather, crystalline lens, cartilage, bone, tooth, muscle tissue, fatty tissue, elastic tissue, nerve tissue—are products of cellular differentiation. The conclusion he drew from this observation was that “elementary parts,” although quite distinct in a physiological sense, may be developed according to the same laws. The elementary parts of most tissues, when traced back from their state of complete development to their primary conditions, are only developments of cells.

In the third part, of a philosophical nature. Schwann, on the basis of his cell theory expounded in the first two parts, developed a theory of the cells that he presented as purely hypothetical. He stated that according to the cell theory, one may suppose that an organized body is not produced, as was accepted by theological theories, by a fundamental power guided in its operation by a definite idea, but is developed, according to blind laws of necessity, by powers that, like those of inorganic nature, are established by the very existence of matter. He believed that the source of life phenomena resided in another combination of the materials of the inorganic world, whether it be in a peculiar mode of union of the atoms to form molecules, or in the arrangement of these conglomerate molecules to form the parts of organisms.

Schwann stated that two groups of phenomena attend the formation of cells: those relating to the combination of molecules to form a cell (plastic phenomena) and those resulting from chemical changes in the component particles of the cells (metabolic phenomena). The cell attracts particles from its medium, which is not a mere solution of cell material but contains this material in other combinations, and it produces chemical changes in these particles. In addition, all the parts of the cell itself may be chemically modified during the process of its growth by a “metabolic power” that is an attribute of the cell itself; this is demonstrated by alcoholic fermentation, which provides a representation of the process that is repeated in all the cells of an organism. Metabolic changes occur not only in the cell contents but also in the solid parts, for example, the nucleus and the membrane. The metabolic processes, in which heat is evolved, are produced only at certain temperatures. All cells demonstrate respiration, a fundamental condition of metabolism; and each cell produces chemical changes in particular organic substances.

Schwann discerned a relation between the phenomena of cell formation, as he conceived it, and the phenomena of crystallization, a comparison developed at length, but only as a hypothesis.

Schwann defined his attitude toward the vital force, as it was accepted by Müller, who proposed the notion of the proper energy of tissues, thus:

A simple force different from matter, as it is supposed, the vital force would form the organism in the same way as an architect constructs a building according to a plan, but a plan of which he is not conscious. Furthermore, it would give to all our tissues that which is called their proper energy, that is, the properties that distinguish living tissues from dead tissues: muscles would owe it their contractility, nerves their irritability, glands their secretory function. Here, in a word, is the doctrine of the vitalist school. Never was I able to conceive the existence of a simple force that would itself change its mode of action in order to realize an idea, without, however, possessing the characteristic attributes of intelligent beings. I have always preferred to seek in the Creator rather than in the created the cause of the finality to which than in the created the cause of the finality to which the whole of nature evidently bears witness; and I have also always rejected as illusory the explanation of vital phenomena as conceived by the Vitalist school. I laid down as a principle that these phenemena must be explained in the same way as those of inert nature [Manifestations en l’honneur de M. le professeur Th. Schwann...].

Schwann sought to replace theological explanation with physical explanation with physical explanation. For him the phenomena of life were not produced by a force acting according to an idea, but by forces acting blindly and with necessity, as in physics. Individual finality, as it was observed in each organism, was determined in the same manner as in inert nature: its explanation depended entirely upon the character istics of matter and upon the characteristics of matter and upon the blind forces with which it had been created by an infinitely intelligent being.

Schwann found the confirmation of this view in the notion of the uniformity of the texture and the growth of animals and plants, as he developed it in his cell theory, “The uniformity of this development demonstrate that it is the same force that it is the same force that everywhere unites molecules into cells, and that this force could be nothing but that of molecules or atoms: the fundamental phenomenon of life there fore had to have its raison d’être in the properties of atoms.” The error suggested to Schwann by Schleiden—the formation of cells within a blastema, which Schwann tentatively compared to the phenomenon of crystallization—satisfied his chemical and physical preferences to such a high degree that one can understand a little more easily why he accepted it on the strength of arguments as weak as those he presented to demonstrate it: those concerning an alleged preexistence of the nucleus in the cartilages, for example.

The solution to the philosophical problem of finality proposed by Schwann transferred it from biology to the universe and its constituent particles, and from the vital force to the Creator. It continued to be influential philosophically, and Lotze was notably inspired by it in his celebrated article on the nature of life, “Leben, Lebenskraft” (1842). Schwann’s cell theory can be regarded as marking the origin in biology of the school of mechanistic materialism that Brücke, du Bois-Rey-mond,Helmholtz, and Carl Ludwig made famous According to Schwann, the theory that led from the molecule (the molecule of the chemist) to the organism by way of the universal stage of the cell, was inspired by an intellecutal, mechanistic reaction to Müiler’s vitalism. Erroneous as it appears now in certain of its aspects, this theory led him to the inestimably significant discovery of the development of organisms through cellular differentiation.

Schwann’s short and brilliant scientific career extended from 1834 to 1839, after which he abandoned rationalism and became a mystic. The scientists gave way to the professor, the inventor, and the theologian. The beginning of this transformation dates from the attacks directed at Schwann by the chemists. Having shown an exceptional insensitivity to epistemological obstacles during his years of fruitful work, he nevertheless succumbed to a particularly violent attack dictated by one of these obstacles. At the beginning of 1839, there appeared in the Annalen der Pharmacie, following a translation of a general paper by Turpin on the mechanism of alcoholic fermentation considered as a result of the activity of yeast, an article entitled “Das enträthselt Geheimnis der geistigen Gährng,” The work of Wöhler, embellished by Leibig with some particularly ferocious touches, this satirical text presented a caricature of the views of Cagniard, Schwann, and Kützing on the role of yeast in alcholoic fermentation.

According to this facetious article, yeast suspended in water assumes the form of animal eggs that hatch with an unbelievable rapidity in a sugary solution. These animals, in the shape of an alembic, have neither teeth nor eyes but do have a stomach, an intestine, an anus (in the form of a pink dot), and urinary organs. Immediately upon leaving the eggs, they throw themselves on the sugar and devour it; it penetrates their stomachs, is digested, and produces excrements. In a word, they eat sugar, expelling alcohol through the anus and carbonic acid through the urinary organs. Moreover, their bladder has the shape of a champagne bottle.

Shortly afterward, a lengthy memoir by Liebig appeared in the same periodical. In it he formulated the theory of alcoholic fermentation as the result of instability produced in sugar by the instability of a substance formed through the access of air to the nitrogenous substances of plant juices. This theory enjoyed a long popularity among chemists, and it was not until Pasteur that justice was done to Cagniard, Schwann, and Kützing. The cruel treatment of Schwann by the scientific leaders of his time made it impossible for him to pursue a scientific career in Germany.

At the same time Schwann’s ardent rationalism grew lukewarm; he became preoccupied with religious meditations, doubtless fostered by the influence of his brother Peter, a theologian. The brother was the author (under the pseudonym Dr. J. F. Müller) of an edition of The Imitation of Christ. His failure in his candidature for a chair at the University of Bonn, added to his other disappointments, sent Schwann into exile in 1839. when he became professor of anatomy at Louvain. But the mainspring of enthusiasm and discovery was broken. Like Pascal before him, he abandoned rationalism to return to the God of his childhood, the “God of the heart, not of reason.” A conscientious professor at Louvain and at Liège (from 1848), Schwann spent the rest of his life in a solitary existence darkened by episodes of depression and anxiety.

Before he went to Liège in 1848, Schwann had been approached by his friend F. A. Spring, who presented the proposals of the Belgian government, including a substantial increase of salary and the promise, never fulfilled, of the construction of an institute of anatomy. When Schwann was appointed, he first received the chair of anatomy, which previously had been held by Spring, who also taught physiology. In 1858 Spring became professor of general pathology and clinical medicine, and Schwann of physiology as well as of general anatomy and embryology. In 1872 he abandoned general anatomy and in 1877 embryology, teaching only physiology until he retired in 1879.

During his stay at Louvain (1839–1848). Schwann developed a method of utilizing the biliary fistula for the study of the role of bile in digestion, and concluded that a lack of bile secretion in the digestive tract is incompatible with survival. He received the sömmering Medal (1841); and in and in 1847 the Sydenham Society published an English version of his Mikroskopische Untersuchungen, translated by Henry Smith, who in his introduction presented the following judgment: “The treatise has now been seven years before the public, has been most acutely investigated by those best competent to test its value, and the first physiologists of our day have judged the discoveries which it unfolds Worthy to be ranked among the most important steps by which the science of physiology has ever been advanced.”

The papers of 1844 and 1845 that record Schwann’s work on the biliary fistula were his last physiological works. After that time, although he never ceased to work in the laboratory, his scientific inquiry lost its impact. Following his arrival in the prosperous industrial region of Liège, he became more of an inventor, developing a number of instruments used in mining technology, including pumps for the aspiration of water in coal mines and a respiratory apparatus for rescue operations. This instrument is the ancestor of the apparatus for measuring metabolism in man and of the devices used by divers.

Schwann’s religious meditations occupied most of his time after his arrival at Liège. He composed what he intended to be a complement to the three parts of the Mikroskopische Untersuchungen, starting from the definition of the atom and extending the cell theory to a general system of organisms, including psychology and religion. His Theoria consisted of the three parts of the Mikroskopische Untersuchungen and of still unpublished chapters; a fourth part was two chapters on irritability and on brain function, and a fifth part concerned the theory of creation. The fourth and fifth parts are purely theological and philosophical. After his retirement Schwann remained in Liège, where he had formed many friendships. His life was troubled by very few incidents, the main one being the case of the “stigmatized” Louise Lateau. High Church authorities having wrongly interpreted what they considered to be a testimonial by him in favor of the miraculous nature of the phenomena. Schwann was forced to publish a statement of rectification.

During a Christmas visit to a brother and sister living in Cologne, he suffered a stroke and died on 11 January 1882, after two weeks of agony, during which he several times expressed the regret that he had not been able to publish the whole of his Theoria.

BIBLIOGRAPHY

I. Original Works. Schwann’s earlier writings include De necessitate aëris atmospherici ad evolutionem pulli in ovo incubito (Berlin, 1834); “Uber die Nothwendigkeit der atmosphärischen Luft zur Entwicklung des Hühnchens in dem bebrüteten Ei,” in Notizen aus dem Gebiete der Natur-und Heikunde, 41 (1834), 241–245; Johannes Müller, Handbuch der Physiologie des Menschen, 2 vols. (Koblenz, 1834–1838), Passim: reports by Schwann on his research on muscle structure, ends of motor nerves, laws of muscle contraction, walls of capillary vessels, contractility of arteries, division of primitive nerve fibers, regeneration of cut nerves, nerve conduction, movements of lymph in the mesentery, ciliary movements, erectile tissues: “Gefässe,” Hämatosis,” “Harnsekretion,” “Hautesekretion,” in Encyclopädisches Wörterbuch der medizinischen Wissenschaft. XIV (Berlin. 1836): “Versuche über die Künstliche Verdauung des geronnenen Eiweisses,” in Archiv für Anatomie und Physiologie (1836), 66–90, written with Müller; “Über das Wesen des Verdauungsprocesses,” ibid., 90–119; “Über die feinere Nervenausbreitung im Schwanze von Froschlarven,” in Medizinische Zeitung, 6 (1837), 169: “Verdauung,” “Muskelkraft,” “Generatio equivoca,” in Oken’s lsis (1837), no. 5. 509–510: no. 6, 523–524; and no. 7. 524, respectively: “Vorläufige Mittheilung betreffend Versuche über Weingährung und Faäulnis,” in Annalen der Physik und Chemie. 41 (1837), 184–193: preliminary notes on the cell theory in Neue Notizen aus dem Gebiete der Naturund Heilkunde, no. 91 (1838), 34–36; no 103 (1838), 225–229; no 112 (1838), 21–23; Mikroskopische Untersuchungen über die Übereinstimmung in der Struktur und dem Wachstum der Thiere und Pflanzen (Berlin, 1839), also in English (London, 1847) and Russian (Moscow, 1939), and repr. as no. 176 of Ostwald’s Klassiker der Exakten Wissenschaften (Leipzig, 1910); and “Übersicht Über die Entwicklung der Gewebe,” in R. Wanger, Lehrbuch der Physiologie, I (Leipzig, 1839), 139–142.

During the 1840’s and 1850’s Schwann published “In structions pour l’homme,” in Bulletin de l’Académie royale de Belgique, 9 (1842), 120–137; “Recherches microsopiques sur la conformité de structure ed d’accroissement des animaux et des plantes,” in Annales des sciences naturelles, Zoologie, 2nd ser., 17 (1842), 5–19; “Mensuration d’organes,” in Nouveaux mémoires del’Académie royale de Belgique, 16 (1843), 552, and 18 (1845), 145:“Versuche um auszumitteln, ob die Galle im Organisus eine für das Leben wesentiliche Rolle spielt,” in Archiv für Anatomie, Physiologie und wissenschaftliche Medicin (1844), 127–159: “Expéconomie aniomale un rêle essentiel pour la vie,” in Nouveaus méBelgique 18 (1845), 3–29; a letter to Wanger concerning his last experiments on the biliary fistula, in R. Wagner, Handwörterbuch der Physiologie, III (Brunswick, 1846), 837: “Sur des graines tombées de l’air dans la Prusse rhéname,” in Bulletin de l’Académire royale de Belgique, 19 (1852), 5–6: anatomie du corps humain, 2 vols. (Brussels, 1852); Rapport sur la situation exception exceptiopnnelle dans laquelle s’ est trouvée la province de Liépoque de l’épidemie cholérique de 1854 et 1855 (Liége, 1857); and ?Erklärung der stöchiometrischen Tael (Cologne, 1858).

Schwann’s latest works include “Réponse á l’interpretation de M. d’Omalius relative á la force vitale,” in Bulletin de l’Académie royale des sciences de Belgique, 24 (1870), 683; “Notice sur Frédéric-Antoine Spring,” in Annuaire de l’Académie royale de Belgique (1874); Mein Gutachten iiber die Versuche die an der stigmatisirten Louise Lateau am 26. Márz 1869 angestellt wurden (Cologne-Neuss, 1875); “Appareil permettant de pénétrer et de vivre dans un milieu irrespirable,” in Bulletin du musée de l’industrie de Belgique, 21 (1877), 5–9; and DDescription de deux appareils permettant de vivre dans un milieu irrespirable (Liége, 1878), repr. in Revue universelle des mines, de la métalurgie, des travaux publics, des sciences et des arts appliqués á l’honneur de M. le professeur Th, Schwann, Liége, 23 juin 1878. Liber memorialis publié par la Commission organisatrice (Düsseldorf, 1879), which contains Schwann’s reply to speeches of congratulation.

II. Secondary Literature. See M. Florkin, Théodore schwann et les débuts de la médecine scientifique (Paris, 1956), Conférences de Palais de la Découverte, ser. D. no. 43; Naissance et déviation de la théorie cellulaire dans l’oeuvre de Théodore Schwann (Paris, 1960); Lettres de Théodore schwann (Liège, 1961); and “Théodore Schwann. 1810–1882,” in florilége des sciences en Belgique (Brussels, 1968): L. Fredericq. Théodore Schwann, sa vie et ses travaux (Liège, 1884); A. Le Roy. “Schwann. Theodore,” in L’Universite de Li-cue depuis sa fondation(Liege, 1869), 919–938: and R. Waterman, Theodor Schwann, Leben und Werk (Düsseldorf, 1960).

Marcel Florkin