Pflüger, Eduard Friedrich Wilhelm

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(b. Hanau, Germany, 7 June 1829; d. Bonn, Germany, 16 March 1910)


Pflüger’s father, Johann Georg Pflüger, began his career as a businessman and commercial traveler. Later he became a passionate politicaian and leader of the democrats in Hanau. He was a combative person and repeatedly came into conflict with government agencies; in the period 1841–1843 he became involved in a high treason trial. In 1848 he was active in the Frankfurt Vorparlament. He studied law in his later years in order to participate in political proceddings, and in 1848 he founded his own political journal. His wife, Charlotte Whilhemine Richter, died in 1855. On his mother’s side Pflüger was descended from Huguenots who had immigrated to Hanau from Dauphiné. He married Christine Marc of Wiesbaden in 1869. They had three daughters, Anna (who later married the chemist Richard Anschütz), Rosa, and Hildegard.

Pflüger, who usually signed his name simply as Eduard, spent his childhood years in Hanau and attended the Gymnasium there. His youth was overshadowed by political developments. He himself became a possionate democrat in 1848, but only for a short time. When he was arrested with rebellious Heidelberg students in 1849, he abandoned politics and law, which he had been studying at Heidelberg since the summer term of 1849, and took up the study of medicine.

In the summer term of 1850 he became a medical student at Marburg, and in 1851 he continued his medical studies at Berlin. There he became an admirer and student of Johannes Müller. In his student years he worked in Müller’s laboratory and attended lectures given by Müller and Emil du Bois-Reymond. He once witnessed a demonstration of the inhibitory effect of the vagus nerve on the heart in Müller’s laboratory. As a result he had the auspicious idea of seeking similar inhibitory effects on the intestine, which he discovered in the rabbit. On the basis of this work he received the M.D. under Müller in 1855. He had already earned such a degree in 1851 at Giessen for a dissertation, dedicated to Müller, dealing with the reflex and psychical capacities of the spinal cord of the frog. This work, written at the age of twenty-two, was his first scientific publication. Pflüger studied this question several more times during his career.

Pflüger’s work on electrotonus qualified him as a university lecturer under du Bois-Reymond at the end of 1858, a few months after Müller’s death. Pflüger worked mostly at his own residence, although under the supervision of du Bois-Reymond, the founder of scientific electrophysiology. Electrotonus was, methodologically considered, a very difficult topic. Pflüger was able to determine the basic laws of the changes in sensitivity that take place in a section of nerve subjected to a direct current from a cathode and from an anode which, due to polarization, spreads “extrapolarly.” The laws proved to be dependent on the polarity, the direction, and the strength of the direct current. This finding, known as Pflüger’s law of convulsion, was required learning for German medical students until the middle of the twentieth century. The principles of the diagnostic and therapeutic applications of the galvanic current in medicine are based on it.

Pflüger’s early reserches revealed his exceptional sagacity, perseverance, and experimental exactness. Because of these qualities, on 28 February 1859 he received the chair of physiology at Bonn, succeeding Helmholtz. Helmholtz had recommended him to the Bonn facutly by stating: “Concerning physiology, among the younger pure physiologists, Pflüger in Berlin appears to me to be the most talented and promising.” In his new post Pflüger was given little in the way of space or resources. Helmholtz had been responsible for both anatomy and physiology, but Pflüger assumed only the physiological duties. He used not the old anatomy building in the Hofgarten (built in 1824) but the so called pavilion, a cramped building in the northesat corner of the university, where a provisional laboratory was constructed for his use. The initially modest facilities caused Pflüger to direct his research ot histology. He studied the embryonal development of the the ovary (1861–1863), the nerve endings in the salivary glands (1866), and the gas exchange in the blood and in the cells. He developed a gas evacuation pump for this purpose (1864–1865).

In his investigation of the ovary Pflüger also studied the question of whether the egg cells originate by division or “in free cell formation.” Pflüger saw the embryonal ovary built up from hollow tubular sacs (“Pflüger’s Tubes “) in the lumina of which were closely packed, bright vesicles, which were probably cells. In these sacs he thought the oogonia could be seen. The endings of secretory nerves, he believed, entered directly into the secreting cells.

Pflüger’s studies of gas exchange continued for many years and encountered extraordinarily great methodological difficulties. Before Pflüger’s time it had not been established whether the oxidizing processes of combustion whether the oxidizing processes opf combustion take place in the lungs (Lavoisier), in the blood (Müller), or in the cells. He succeeded in demonstrating that cellular activity, or the energy requirement of the cell, determines the magnitude of the oxygen consumption; the blood respires comparatively little. In related work, Pflüger’s experiment on the “table-salt frog” became famous: a frog in which the blood was replaced by a physiological salt solution displayed no significant decrease in gas exchange.

The concept of the “respiratory quotient” was also developed by Pflüger. He conducted new studies to show that the exchange of gas in the lungs and tissues results exclusively from the fall in partial pressure of the gases and cannot be considered as a secretion. That the respiratory action is stimulated by a surplus of carbon dioxide and a lack of oxygen was another definitive result of his work. His famous work, “Uber die physiologische Verhrenung in den lebenden Organismen” (Pflüger’s Archiv, 10 [1875], 251–367), consolidated these studies, which subsequently led Pflüger to consider the maintenance of heat in cold surroundings. He fund that cold was the most effective stimulus to the increase of metabolism. He localized this process—through the application of cuare—in the musculature. This finding also remains valid today.

Another field that claimed Pflüger’s attention for several decades was the metabolism of the nutritive substances: protein, fat, and carbohydrates. He published more than sixty works on glycogen alone. Yet, despite the greatest exactitude in his methods, his determination of nitrogen-bearing substances had no unqualified success. He erroneously saw in protein alone the “source of the muscular force,” and he considered protein in general to be the only nourishing substance. In fact he held this position on the basis of the hypothesis that the secret of living matter lies in the molecular structure of protein. His finding that the quantity of protein ingested determines the amount of decomposition of protein in the body has proved to be correct. Thus he did not believe that glycogen could be produced from protein. He became involved in violent controversies over this matter, especially with Voit’s school in Munich. Shortly before his death, however, he became convinced of his error.

Pflüger expended much time, energy, and inventiveness on the improvement of methods for dertermining glycogen. In opposition to most other researchers, he believed that pancreatic diabetes was a nervous distrubance. In a letter (1896) to his daughter we find the complaint: “Glycogen is still the dream of my darys and nights. It’s dreadfu.” The result of this work was a large book, Das Glykogen und seine Beziehunhgen zur Zuckerkrankheit (2nd ed., 1905). Containing over five hundred pages, it included a review of the entire world literature on this subject, which was cited and utilized precisely. He died of a liver carcionoma at the age of eighty-one.

Pflüger was only of medium stature but powerfully built. His large beard gave him a commanding appearance. He was humane, rather reticent, and even shy when away from the Institute or his family. Pflüger attended few congresses, but he exercised a strong influence on his contemporaries while serving as editor of Archiv fur die gesamte physiologie des Menschen und der Tiere from 1868. Few people went as far as Pflüger in public criticism of the works of others, and he was the most feared critic of his time. His remarks could even degenerate into personal abuse; and when it was a matter of eliminating errors, he knew no restraint. He demanded the highest standards of diligence, exactness, and conclusiveness in his demonstrations. His polemic against Voit, Hermann Munk, Hermann Senator, and others was caustic beyond all measure. “Criticism is the most important motive of progress; for that reason I practice it,” he stated (see Archiv, 222 [1929], 561.) His lectures were origninal and stimulating but not easy.

Pflüger loved his family above all else. He enjoyed taking long hikes with his wife and daughters and was exceedingly concerned about his health and theirs. He was a Christian but did not belong to any church. He claimed countless animals for experimental purposes—156 dogs in the last year of his life alone. Despite his respect for living creatures, the desire for knowledge took precedence. His wife once sighingly remarked that she had constantly had a very powerful rival, science.

As much a Pflüger regarded hypotheses as necessary in his discipline and sometimes even made far-reaching use of them, to htat same degree he confined his work to physiology and to the questions of the life sciences that are open to experiemnt. He viewed the living being as a great unity, full of both teleology and mechanism (Archive, 15 [1877], 57–103). He reserved his greatest reverence for Aristotle, whose likeness hung over his desk. Pflüger attributed the unifying forces in the organism to the nervous system. He thus rejected the the nervous system. In his article “über den elmentaren Bau ds nervensystems” (Archive, 112 [1906], 1–40) he expressed himself emphatically on this point. His articles constantly demonstrated an intensive study of the literature and even a careful study of originial sources already historical in his day. For this reason his works are frequently useful reading even today.

Pflüger was strongly opinionated. He called himself a student of Müller, but not of du Bois-Reymond, with whom he had worked the longest. His relations with du Bois-Reymond were not always untroubled. He seems to have had no friend among the physiologists, and his only lifelong friend was the botanist N. Pringsheim.

Pflüger was a member of the Leopoldina and honorary member of many foreign academies; he also was awarded the order Pour le mérite. He was rector at Bonn in the academic year 1889–1890.


I. Original Works. Pflüger’s works include “De functionibus medullae oblongatae et spinalis psychicis” (M.D. diss., Gissen University, 1851); Die sensorischen Funktionen des Ruckenmarks der Wirbeltiere nebst einer neuen Lehre von den Leitungsgesetzen der Reflexionen (Berlin, 1853); “De nervorum planchnicorum functione” (M.D. diss., University of Berlin, 1855); Das hemmungsnervenststem für die peristaltische Bewegung der Gedärme (Berlin, 1857); Untersuchungen uber die Physiologie des elktgrotonus (Berlin, 1859); Uber die Eierstocke derSäugethiere und des Menschen (Leipzig, 1863); Über die Kohlensäure des Blutes (Bonn, 1864); “Beschreibung meiner Gaspumpe,” in Untersuchung aus dem physiologischen Laboratorium zu Bonn (Berlin, 1865), 183–188; Die Endigungen der Absonderungsnerven in den Speicheldrüsen (Bonn, 1866); “Uber die physiologische Verhrenung in den lebenden Organismen,” in Pflügers Archiv für die gesamte Physiologie des Menschen und der Tiere, 10 (1875), 251–367.

Subsequent writings are “Die teleologische Mechanik der lebendigen Natur,” in Pflügers Archiv für die gesamte Physiologic des Menschen and der Tiere, 15 (1877), 57–103; “Die Physiologie und ihre Zukunft,” ibid., 361–365; “Wesen und Aufgaben der Physiologie,ibid., 18 (1878), 427–442, the inaugural address at the Physiological Institude at Bonn-Poppelsdorf, 9 Nov. 1878; Die allgemeinen Lebenserscheinungen (Bonn, 1889), his rectorial address at Bonn; Über die Kunst der Verlängerung des menschlichen Lebens (Bonn, 1890), oration delivered on the Kaiser’s birthday; “Das Glykogen und seine Beziehungen zur Zuckerkrankheit,” in Pflügers Archiv für die gesamte Physiologie des Menschen und der Tiere, 96 (1903), 1–398, published as a book (Bonn, 1905); and “Über den elementaren Bau des Nervensystems,” in Pflügers Archiv für die gesamte Physiologie des Menschen und der Tiere, 112 (1906), 1–40.

II. Secondary Literature. On Pflüger and his work see A. Bethe, “E. Pflüger als Begründer dieses Archives,” in Pflügers Archiv für die gesamte Physiologie des Menschen und der Tiere, 222 (1929), 569–572; W. Bleibtreu, “Pflügers Persönlichkeit,” ibid., 562–568; W. Haberling and S. Pagel, “Pflüger, Ed. Fr. W.,” in Biographisches Lexikon der hervorragenden Ärzte aller Zeiten und Vülker, 2nd ed., IV (Berlin–Vienna, 1932), 586–587; E. Heischkel, “Eduard Pflüger (1829–1910). Physiologe,” in Lebensbilder aus Kurhessen und Waldeck, 1830–1930, I. Schnack, ed., IV (Marburg, 1950), 253–263—Lebensbilder . . . is no. 20 of Veröffentlichungen der Historischen Kommission für Hessen und Waldeck; M. Nussbaum, E. F. W. Pflüger als Naturforscher (Bonn, 1909), with partial bibliography; R. Rosemann, “Pflügers Lebnswerk,” in Pflügers Archiv für die gesamte Physiologie des Menschen und der Tiere, 222 (1929), 548–562; K. E. Rothschuh, Entwicklungs-geschichte physiologischer Endeckungen in Tabllenform (Munich, 1952), nos. 137, 140, 221, 225, 227, 250, 603, 640, 677, 680, 721, 724, 748, 782, 941, 1000, 1032, 1317, 1392; and Geschichte der Physiologie (Berlin, 1953), esp. 133–134; F. Runkel, “Eduard Pflügers Vorfahren und Jugendzeit,” in Pflügers Archiv für die gesamte Physiologie des Menschen und der Tiere, 222 (1929), 572–574; and K. Schmiz, Die medizinische Fakultät der Universität Bonn 1818–1918. Ein Beitrag zur Geschichte der Medizin (Bonn, 1920), 26–29.

Obituaries are by Réne du Bois-Reymond in Berlinger klinische Wochenschrift, 47 (1910), 658–659; H. Boruttau in Deutsche medizinische Wochenschrift, 36 (1910), 851–852; E. von Cyon in Pflügers Archiv für die gesamte Physiologie des Menschen und der Tiere, 132 (1910), 1–19; J. A. F. Dastre in Comptes rendus des séances de la Société de biologie, 68 (1910), 648–650; H. Leo in Münchener medizinische Wochenschrift, 57 (1910), 1128–1129; F. Schenck in Naturwissenschaftliche Rundschau (1910), 340; and A. D. Waller in Nature, 83 (1910), 314.

Additional material may be found in the archives of the Institut für GFeschichte der Medizin, Münster University.

K. E. Rothschuh