Dubois-Reymond, Emil Heinrich

(b. Berlin, Germany, 7 November 1818; d. Berlin, 26 December 1896)

etectrophysiology.

Emil’s father, Felix Henri du Bois-Reymond, moved from Neuchâtel, Switzerland (then part of Prussia), to Berlin in 1804 and became a teacher at the Kadettenhaus. Later he was the representative from Neuchâtel to the Prussian government, and in 1832 he published a fundamental work on linguistics. His orthodox Pietism and authoritarian manner soon aroused his son’s spirit of resistance. Emil’s mother, the former Minette Henry, was the daughter of the minister who served the French colony in Berlin and the granddaughter of Daniel Chodowiecki, a wellknown artist. Emil had two sisters, Julie and Felicie, and two brothers; his brother Paul became a distinguished mathematician. The family’s background made them feel that they belonged to the French colony in Berlin. They usually spoke French at home; and Emil attended the French academic high school in Berlin, except for a year in Neuchâtel.

In 1837 du Bois-Reymond began his studies at the University of Berlin, where, at first, somewhat undecided about his future, he attended lectures in theology, philosophy, and psychology. During a short period at the University of Bonn (1838–1839), he studied logic, metaphysics, and anthropology, in addition to botany, geology, geography, and meteorology. In the winter semester of 1839, having returned to Berlin, he was inspired by Eduard Hallmann, assistant to the anatomist Johannes Müller, to study medicine. It was also Hallmann who taught him the basic principles of osteology and botany and worked out a schedule of the lectures he should attend. His letters to Hallmann are splendid proof of du Bois-Reymond’s intellectual liveliness, but they also show his initial uncertainty about his course of study and his own talents. He was easily influenced and was able only slowly to eradicate the prejudice for Müller that he had acquired from Hallmann.

Du Bois-Reymond was soon acquainted with such teachers and researchers as Heinrich Dove, Theodor Schwann, and Matthias Schleiden, and became a close friend of Ernst Brücke, Hermann Helmholtz, Carl Reichert, and Carl Ludwig. In 1840 he worked more closely with Müller, concerning himself with anatomical preparations, comparative anatomy, physiology, and microscopy. He was still very interested in morphology. During this period he also studied the philosophical writings of Hegel and Schelling with great interest and attended the clinical lectures of Dieffenbach and Johann Schönlein, among others.

On 10 February 1843 du Bois-Reymond received his degree with a historical-literary paper on electric fishes. This was a subsidiary result of his interest in the history of animal electricity and also a preliminary study for the experimental verification, recommended to him by Müller, of the new papers of Carlo Matteucci, who in 1840 had published his Essai sur les phénomènes électriques des animaux. This marked the start of his lifelong, almost monomaniacal experimental analysis of animal electricity. It occupied him constantly from 1840 to 1850; and in the course of his work he developed a strong preference for experimental physics, particularly the application of physical principles and methods of measurement to the problems of physiology. He was encouraged greatly in this by Brücke and later by Helmholtz. On 14 January 1845 he founded the Physikalische Gesellschaft with Brücke, Dove, and others in Berlin. In December 1845 he met Helmholtz and was deeply impressed by him.

Du Bois-Reymond’s first experimental and theoretical investigations of animal electricity produced definite conclusions in November 1842. Upon Müller’s advice the results were hurriedly submitted for publication in Poggendorff’s Annalen der Physik und Chemie, appearing as “Abriss einer Untersuchung über den sogenannten Froschstrom und über die electrischen Fische” in January 1843. Through Humboldt he also sent an extract to the Académie des Sciences in Paris.

On 6 July 1846 du Bois-Reymond qualified as a university lecturer with the paper “über saure Reaktion des Muskels nach dem Tode.” He had already completed a great deal of the manuscript of Untersuchungen über thierische Elektrizität, mainly the preface of volume I (which became famous), the historical introduction, and the techniques of electrophysiology. From 1848 to 1853 du Bois-Reymond was instructor in anatomy at the Berlin Academy of Art. He did not lecture at the university until 1854, when Müller asked him to lecture on physiology with him. Du Bois-Reymond was now concerned exclusively with physiology, and with his friends Brücke, Ludwig, and Helmholtz he became a pioneer in the new physical orientation of the field, which sought to explain all processes in an organism by means of physical, molecular, and atomic mechanisms, without drawing upon hypothetical vital forces.

Thanks to the great interest which Humboldt had had in galvanism since his youth, du Bois-Reymond was elected to membership in the Prussian Academy of Sciences in 1851, at the age of thirty-three. From 1876 he was one of the permanent secretaries of the academy, and a great part of his work was dedicated to preparing the meetings and the official speeches for the annual celebrations in memory of Leibniz, its founder, and of its great patron, Frederick II.

In 1853 du Bois-Reymond married Jeanette Claude. They had four sons and five daughters. Of the four sons, René became a physician and a physiologist, Claude an ophthalmologist, and Allard and Felix mathematicians and engineers. Of the daughters, Estelle gained fame by editing her father’s post-humously published works.

In 1855 du Bois-Reymond was named associate professor. When Müller died suddenly in 1858, the chair was divided. Reichert received the professorship of anatomy and du Bois-Reymond that of physiology. Now he had to carry the entire burden of lecturing as well as a heavy schedule of academy duties. At this time the physiology department was located in the west wing of the university building on Unter den Linden; along with the anatomy department and the museum, there were a few shabby rooms, inadequate for the needs of the physiology department. The conditions for experimentation were so unsuitable that du Bois-Reymond had to conduct the greater part of his experiments in his own apartment. Only after long efforts was a new institute for physiology, located on the Dorotheenstrasse, completed in 1877; after Carl Ludwig’s institute in Leipzig it was the largest and most modern in Germany. There were four departments: physiological chemistry (Eugen Baumann, Kossel), physiological histology (Gustav Fritsch), physiological physics (Arthur Christiani), and a special department for experimentation with animals (Karl Hugo Kronecker, J. Gad). Also at this time the Archiv für Anatomie, Physiologie und wissenschaftliche Medizin, which had been taken over from Müller and since then edited by Reichert and du Bois-Reymond, was divided into an anatomical section and a physiological section, the latter being edited by du Bois-Reymond. Most of the papers by his colleagues and pupils appeared in this journal, as did most of the publications from Ludwig’s institute in Leipzig. Among du Bois-Reymond’s pupils were Eduard Pflüger, Ludimar Hermann, Isidor Rosenthal, Hermann Munk, F. Boll, Carl Sachs, and Gad, all of whom became prominent physiologists. A great many Russians worked in the institute also. A list of his colleagues and pupils, along with their publications, is in the dissertation by J. Marseille (1967). Du Bois-Reymond gave his colleagues and pupils great personal freedom and latitude to develop on their own, occupying himself almost exclusively with the problems of electrophysiology. After 1877 his publications are dominated by public speeches at the academy and his investigations of electric fishes.

By heritage du Bois-Reymond was particularly open to things French; he sought contact with French colleagues and visited Paris as early as 1850 in order to present the results of his experiments. He also met Claude Bernard there. However, he obviously felt that he did not receive the recognition he had expected. He reproached French researchers for reading only French publications and later leveled harsh criticism against his French neighbors, particularly during the Franco-Prussian War. He got along better with his English colleagues, traveling to England in 1852, 1855, and 1866 to visit or to attend congresses. H. Bence-Jones, who became a good friend and colleague, published a short version of du Bois-Reymond’s papers in 1852.

Du Bois-Reymond was twice rector of the University of Berlin, in 1869–1870 and in 1882–1883. He was of course a member of almost all noteworthy scientific academies. On 11 February 1893 he celebrated the fiftieth anniversary of obtaining his doctorate. The formal address was delivered by Virchow. On 26 December 1896 du Bois-Reymond died of senile heart disease. The eulogy given by his pupil Rosenthal was used as a preface to the second edition of du Bois-Reymond’s speeches (1912). The best biography is by his pupil E. Boruttau but it lacks a bibliography. With du Bois-Reymond, the last of that group died which had led German physiology to its position of uncontested leadership at the end of the nineteenth century.

From the beginning du Bois-Reymond directed his research to electrical phenomena that had been thought to be involved in various life processes since the time of Galvani but were long known to exist with certainty only in the discharges of electric fishes. Along with Galvani and Volta, Humboldt (1797) had concerned himself with these phenomena; this was the reason for his great interest in du Bois-Reymond’s research. Interest in the phenomenon of animal electricity had generally receded since about 1820; but Aldini, Nobili, and particularly Matteucci continued to concern themselves with its explanation and measurement. In 1828 Nobili, using an improved Schweigger multiplier, was able to demonstrate the presence of an electric current courant propre on an intact but skinned frog trunk. From 1836 Matteucci concerned himself with the shock of electric fishes and confirmed the existence of the courant propre. In 1842 he demonstrated the existence of a courant musculaire, the demarcation, or injury, current between the uninjured surface and the cross section of a muscle. Matteucci also observed the “induced contraction” that a nerve-muscle preparation shows when its nerve is laid over the thigh muscle of a second, contracting preparation. In addition, he was the first to observe deflections in the galvanometer when a muscle contracted in strychnine tetanus. His later investigations were published in Untersuchungen über die thierische Elektrizität (1848) and in GesammelteAbhandlungen zur allgemeinen Muskel-und Nervenphysik (1875–1877).

Du Bois-Reymond’s most significant achievement was introducing clear physical methods and concepts into electrophysiology. In 1842–1843 he described (incorrectly at first) an autogenous current from the intact surface of the muscle to the tendon and (correctly) the injury current between the surface and the cross section; he used a multiplier that he had coiled and improved himself. He found this current even in the smallest pieces of muscle and traced it correctly to the individual muscle fibers, the interior of which is negative with respect to the surface of the fibers. The contracting muscle thus reveals a change, the so-called “negative fluctuation” of the injury current (1849). It occurs during every muscle contraction; but during tetanus, which arises from summation of many individual contractions, it becomes much clearer. Du Bois-Reymond confirmed induced contraction and identified it correctly as “secondary contraction” caused by the stimulus that the electric current of a contracting muscle in one nerve-muscle preparation gives to the nerve of a second preparation.

Du Bois-Reymond’s interpretation of the basic molecular processes was analogous to Ampère’s interpretation of the magnet. He believed that the muscle fiber was made up of numerous peripolar electromotive molecules, each thought to consist of a positive equatorial zone and two negative polar zones. For the tendons he assumed electrically neutral parelectronomic molecules. When Hermann was able to demonstrate the lack of current in intact muscle fibers in 1867–1868, du Bois-Reymond tried in vain to save his theory of preexistence by means of additional assumptions. In any case, he interpreted the currents from intact, injured, and contracting muscles as having a single cause.

Because of the extremely high sensibility of his multiplier, he was able in 1849 to show the injury current also in the nerve. He succeeded further in demonstrating the “negative fluctuation” in tetanized nerves and thus proved the electric nature of the Nervenprinzip.

Du Bois-Reymond also discovered that polarization occurs at the points of entry and exit during the flow of direct current through a nerve. It is shown in a change of charge at and near the positive and negative poles of the section through which the current flows. This “electrotonus” was the subject of his work for many years, and his pupil Pflüger continued to investigate the subject intensively. In connection with this du Bois-Reymond proposed the thesis that the effect of the electrical stimulation, apart from the polarization, depends upon the slope of the change in intensity of the current at the point of stimulation, and not upon the duration or the absolute intensity of the current. After 1869, when Wilhelm Krause developed the theory that the transmission of stimulation from nerves to the muscle fiber is the result of an electrical discharge of the end plate, du Bois-Reymond also pursued these questions. He considered it possible for a chemical mechanism for transmitting stimulation to exist along with the electrical mechanism.

Quite a large part of du Bois-Reymond’s research concerned the explanation of the nature and origin of the shock given by electric fishes. Many papers, particularly after 1877, written with Sachs and Fritsch are concerned with the anatomy and the production of electricity in these creatures. From 1857 he studied living examples of the Malapterurus electricus (electric catfish), the torpedo, and the Gymnotus electricus.

Du Bois-Reymond owed his great scientific success to the development of new electrophysiological methods of deriving and measuring current. He was the first to avoid the many difficulties and sources of error that make it very hard to obtain clear results in electrophysiology, and he created much of the apparatus of electrophysiology. His first multiplier (1842) had almost twice as many wire coils as previous ones, which made it unusually sensitive. In 1849 he once more increased them several times for the measurement of the nerve current. He was also the first to develop a deriving electrode that could not be polarized, by using glass tubes closed with a clay stopper and including a combination of zinc slabs in a solution of zinc sulfate (1859); it remained in use until about 1940. Du Bois-Reymond also was the first to develop the procedure of measuring weak bioelectric currents without loss by means of compensation with a rheochord bus-bar or a handy round compensator (1861). For decades physiologists used the du Bois-Reymond sliding-carriage induction coil for many purposes. The principle of induction had been known since the time of Oerstedt and Faraday. Du Bois-Reymond built an apparatus with a secondary coil that could be moved on a sliding carriage (1849). This made it possible to graduate and calibrate the intensity of the first and last induction shocks. This instrument was the starting point for many devices used in the medical applications of Faradic stimulations in electrotherapy.

Many very useful aids in electrophysiology were developed or adapted to the needs of animal experimentation by du Bois-Reymond. He constructed “simple” switches that guaranteed a definite electrical contact, as well as the mercury switch, the rocker, the electrode holder, stands, and clamps. He was the first to succeed in clarifying, eliminating, or avoiding the many sources of error in electrophysiological procedure, such as losses due to leakage, the polarization phenomena on metal electrodes, the deflection caused by nonparallel muscle fibers, the temporal change in the injury current following death, and the influence of extension on the voltage derived. Du Bois-Reymond also investigated the currents which occur in secretory glands (1851) and believed that he could derive electric currents from the human arm during voluntary contraction.

Most of du Bois-Reymond’s experimental findings and technical procedures have remained valid. Some of his theories and several of the conceptions derived from his incorrect molecular hypothesis (such as denying the absence of current in intact muscles) did not last. Students, co-workers, and visitors from all over the world took up electrophysiology; improved the measuring devices; and demonstrated electrical phenomena in glands, the eye, the heart, and the brain. In this way, new areas of physiology originated from his preliminary work.

Du Bois-Reymond’s interest in molecular physics led him to lecture during almost every summer semester from 1856, on the “physics of organic metabolism.” This involved such processes as diffusion of gases and liquids, diffusion through pores, adsorption, the theory of solutions, capillarity, surface tension, swelling, osmosis, and secretion. The lectures, which were edited by his son René (1900), show du Bois-Reymond’s interest in the subject and make one aware that his intellectual effort belonged completely to the period up to the end of the 1860’s. His last decades were, for the most part, filled with other work and problems that were much less those of physiology than general problems of scientific knowledge, problems of methods and limitations, and historical questions. After about 1870 du Bois-Reymond became increasingly active in the public discussion of the relation between the natural sciences and the humanities, particularly philosophy, theology, and history. He had uncommonly wide knowledge and judgment in both science and various branches of the humanities. This is shown especially by the two-volume Reden.

In France and Germany in the second half of the eighteenth century, the idea had prevailed that the processes of formation, conservation, irritability, sensitivity, and such could not be explained by the laws of inorganic nature. Something like a vital force, a conservative force, or an educative force—analogous to the force of gravity—was supposed to direct the vital processes. Even Müller, du Bois-Reymond’s teacher, subscribed to this belief; thus it was significant when Müller’s young assistant eloquently demonstrated the inconsistencies in this theory: “Matter is not a wagon to which forces can be arbitrarily hitched or unhitched like horses.” Forces do not exist independently of matter; and where they are expressed, they are the same in the living and the dead. At that time Schwann, Hermann Lotze, Brücke, Ludwig, and Helmholtz thought similarly.

Du Bois-Reymond’s detailed, well-documented memorial speech for Müller (1858) is of the greatest historical interest. The same is true of his speech for Helmholtz (1895). His speech at the opening of the new institute for physiology (1877) is also an important document. His speeches on Voltaire (1868), La Mettrie (1875), and Maupertuis (1892) are prime examples of analysis of intellectual history. To him Voltaire was a fighter for intellectual freedom, human dignity, and justice, who had disseminated the significance of Newtonian thought. Du Bois-Reymond also portrayed the astonishing gifts of Diderot (1884), who was equally productive in treatises and novels, in art and science, ethics, metaphysics, philology, and philosophy. He demonstrated in several speeches his excellent knowledge of Leibniz, his philosophy, and his scientific significance. His lively feeling for the history of science was expressed in his address of 1872. He praised the charisma of the master scientists of the past and considered the history of science the most important, but most neglected, part of cultural history.

Du Bois-Reymond’s lecture “Kulturgeschichte und Naturwissenschaft” (1876) contains a complete analysis of Western cultural history in relation to the inductive sciences. He saw the absolute organ of culture in the natural sciences and the true history of mankind in the history of the natural sciences. Man had become a “rational animal who travels with steam, writes with lightning, and paints with sunbeams.” He portrayed the weaknesses of the contemporary schools, which provide classical languages but are deficient in mathematics and the theory of conic sections. His political speeches “Der deutsche Krieg” (1870), “Das Kaiserreich und der Friede” (1871), and “Über das Nationalgefühl” (1878) are not without exaggerated complaints about the self-praise and chauvinistic feelings of superiority of the French.

In any case, du Bois-Reymond was not afraid to express unpopular thoughts. His inaugural speech as rector, “Goethe und sein Ende” (1882), annoyed a great many intellectuals. He mercilessly portrayed the weaknesses of Goethe’s concept of nature, his inclination to deduction, the deficiencies of his theory of color, and even the curious contradictions in his Faust. Du Bois-Reymond maintained that natural science had come as far as it had without Goethe’s scientific writings: one should leave Goethe alone as a scientist.

Other speeches show how well read du Bois-Reymond was and his ability to judge questions of art. The greatest excitement and the most bitter opposition were caused by the two speeches “Über die Grenzen des Naturerkennens” (1872) and “Die sieben Welträtsel” (1880). For him there were two insoluble questions for natural science, that of the essence of matter and force and that of the occurrence of consciousness in connection with molecular processes in the brain. Even an intellect like Laplace would not be able to know all of the factors involved in these questions. The seven riddles of the world are, according to du Bois-Reymond, those questions which science can answer only with the words ignoramus or ignorabimus: (1) the essence of force and matter, (2) the origin of movement, (3) the origin of life, (4) the teleology of nature, (5) the origin of sense perception, (6) the origin of thought, and (7) free will. He considered these questions transcendental.

Du Bois-Reymond’s views annoyed both extreme natural scientists, like Ernst Haeckel, and theologians. The controversy he stimulated filled, the daily press as well as the scientific literature. Accordingly, du Bois-Reymond significantly affected his own time and posterity on two levels. In electrophysiology he laid the foundations of the methods that were used for a century. In his treatment of problems of scientific boundaries and principles, he developed such brilliant formulations that his arguments still arouse great interest.

Du Bois-Reymond had an unusual gift for language and a finely developed sense of beauty, and he chose his words carefully. He loved figurative comparisons; those he used were sometimes audacious but never dull. His language was clear, his thought structure logical. He loved to introduce quotations from both classical and contemporary poets. French heritage blended with German thoroughness, eloquence with awareness of problems. From his youth du Bois-Reymond was receptive to philosophy and religion; but in protest against his Kantian and pious father, he tended very early toward cognitive-theoretical empiricism and free-thinking atheism. His study of La Mettrie had played not a slight role. He had only little love for nineteenth-century Christianity. Metaphysics, he thought, should not be mixed with natural science: the idea of the vital force was a mistake of this kind because the law of the conservation of energy, the framework for all transformations of energy, forbids such a hypothesis.

The neovitalism of Hans Driesch and Gustav von Bunge drew du Bois-Reymond’s sharp condemnation. Thus, as he wrote in 1875, he found in himself a union of “intellectual inclinations which drive me with almost equal intensity in very different directions of perceiving nature.” Du Bois-Reymond, for all his modesty, was self-confident and certain. His intellectual vitality and his many talents allowed him to make friends rapidly. He was uncommonly devoted to his friends, such as Hallmann and Ludwig, and did not allow his co-workers, such as Sachs and Fritsch, to go unrecognized. Understandably, he found it difficult in his old age to encounter much hostility and many refutations of his molecular theory of animal electricity. The opposition of his talented student Hermann was a bitter blow, but the scientific world of the nineteenth century never lacked polemics.

BIBLIOGRAPHY

I. Original. Works. DU Bois-Reymond’s writings include “Vorläufiger Abriss einer Untersuchung über den sogenannten Froschstrom und über die elektrischen Fische,” in Poggendorff’s Annalen der Physik und Chemie, 58 (1843), 1–30; Untersuchungen über thierische Elektrizität, 2 vols. (Berlin, 1849–1884), vol. II in 2 sees., sec, 2 in 2 pts.; and Abhandlungen zur allgemeinen Muskel- und Nervenphysik, 2 vols. (Leipzig, 1875–1877). The books contain many papers that had already appeared in the Monatsberichten..., Sitzungsberichten..., and Abhandlungen der Preussischen Akademie der Wissenschaften and also those that had been published in Poggendorff’s Annalen and in Archiv für Anatomie, Physiologie und wissenschaftliche Medizin. A complete bibliography of du Bois-Reymond’s publications is in the dissertation by J. Marseille (below). The list of academic speeches (incomplete) is in A. von Harnack, Geschichte der Königlichen, Preussischen Akademie der Wissenschaften zu Berlin, III; and in Otto Köhncke, Gesamtregister über die in den Schriften der Akademie von 1700–1890 erschienen wiss. Abhandlungen und Festreden (Berlin, 1900). The 2-vol. 2nd ed. of his Reden, Estelle du Bois-Reymond, ed. (Leipzig, 1912), contains almost all of his public speeches. Further source are Emil du Bois-Reymond. Jugendbriefe an Eduard Hallmann, Estelle du Bois-Reymond, ed. (Berlin, 1918); and Zwei grosse Naturforscher des 19. Jahrhunderts. Ein Briefwechsel zwischen Emil du Bois-Reymond und Karl Ludwig, Estelle du Bois-Reymond and Paul Diepgen, eds. (Leipzig, 1927).

II. Secondary Literature. Accounts based on original sources are H. Bence-Jones, On Animal Electricity, Being an Abstract of the Discoveries of Emil du Bois-Reymond (London, 1852); and Ilse Jahn, “Die Anfänge der instrumentellen Elektrobiologie in den Briefen Humboldts an Emil du Bois-Reymond,” in Medizin historisches Journal, 2 (1967), 135–156. On the history of electrophysiology, see the following by K. E. Rothschuh: “Die neurophysiologischen Beiträge von Galvani und Volta,” in L. Belloni, ed., Per la storia della neurologia italiana (Milan, 1963), pp. 117–130. In addition see “Alexander von Humboldt und die Physiologie seiner Zeit,” in Archiv für Geschichte derMedizin, 43 (1959), 97–113; “Von der Idee bis zum Nachweis der tierischen Elektrizität” ibid., 44 (1960), 25–44; and “Emil du Bois-Reymond und die Elektrophysiologie der Nerven,” in K. E. Rothschuh, ed., Von Boerhaave bis Berger (Stuttgart, 1964), pp. 85–105. Also of value are Giuseppe Moruzzi, “L’opera elettrofisiologica di Carlo Matteucci,” in Physis, 4 (1964), 101–140, with a bibliography of works by Matteucci; and J. Marseille, “Das physiologische Lebenswerk von E. du Bois-Reymond mit besonderer Berücksichtigung seiner Schüler,” an M.D. dissertation (Münster, 1967), with bibliography.

Biographies, memorials, and obituaries are Heinrich Boruttau, Emil du Bois-Reymond, vol. III in the series Meister der Heilkunde (Vienna-Leipzig-Munich, 1922); and I. Munk, “Zur Erinnerung an Emil du Bois-Reymond,” in Deutsche medizinische Wochenschrift, 23 (1897), 17–19, with portrait. Further references to obituaries are in Index medicus, 2nd ser., 2 (1897), 521–522; 3rd ser., 3 (1922), 178.

Further secondary literature and historical evaluations are Erich Metze, Emil du Bois-Reymond, sein Wirken und seine Weltanschauung, 3rd ed. (Bielefeld, 1918); Paul Grützner, in Allgemeine deutsche Biographie, XLVIII (1903), 118–126; Friedrich Harnack, Emil du Bois-Reymond und die Grenzen der mechanistischen Naturauffassung (Festschrift zur 150-Jahr-Feier der Humboldt-Universität Berlin), I (Berlin, 1960), 229–251; F. Dannemann, “Aus Emil du Bois-Reymond’s Briefwechsel über die Geschichte der Naturwissenschaften,” in Mitteilungen zur Geschichte der Medizin und der Naturwissenschaften und der Technik, 18 (1919), 274 ff.; K. E. Rothschuh, Geschichte der Physiologie (Berlin-Göttingen-Heidelberg, 1953), pp. 130–139, with portrait; Wolfgang Kloppe, “Du Bois-Reymond’s Rhetorik im Urteil einiger seiner Zeitgenossen,” in Deutsches Medizin historisches Journal, 9 (1958), 80–82; and Rudolf Virchow, “Ansprache zum 50-jährigen Dr. Jubiläum von Emil du Bois-Reymond,” in Berliner klinische Wochenschrift, 30 (1893), 198–199.

K. E. Rothschuh