(b. Munsterberg, Silesia [now Poland], 19 March 1845; d. Frankfurt am Main, Germany, 4 August 1904), pathology, histology, neurology.
Weigert was born in the same district in Silesia as his cousin Paul Ehrlich, his junior by nine years. The problem of the selective action of dyes on biological materials (microchemical reactions), which led Ehrlich to develop chemotherapy, led Weigert to make revolutionary advances in histological techniques. These advances made it possible for researchers to gain fundamental insights into the fine structure of the central nervous system. Weigert is thus closely associated with brain and spinal cord research and with neurology and psychiatry.
After attending the Gymnasium in Breslau, Weigert studied medicine at the University of Breslau. His teachers included Ferdinand Cohn and Rudolf Heidenhain. Weigert continued his studies in Berlin, where he worked as Virchow’s amanuensis. In 1866 he received his medical degree from the University of Berlin for a dissertation, “De nervorum laesionibus telorum ictu effectis.” Two years later Weigert became an assistant of Waldeyer-Hartz, professor of pathology at Breslau, who undoubtedly strengthened Weigert’s interest in morphology. In 1871 Weigert became clinical assistant to Hermann Lebert, and in 1874 assistant to Julius Cohnheim, under whom he qualified for teaching pathology in 1875. Three years later he followed Cohnheim to the University of Leipzig, where in 1879 he was named extraordinary professor of pathology. For a long time Weigert lectured in place of Cohnheim, who had fallen ill. Cohnheim died in 1884, and when the faculty did not nominate him even as a possible successor, Weigert resigned from his post the following year. He decided to take up medical practice, but he was dissuaded by an offer to become director of the pathological-anatomical institute of the Senckenberg Foundation in Frankfurt. He held this post until his death at age fifty-nine from a coronary embolism. Curiously, he himself had made a major contribution to knowledge of this disease. Weigert never married.
Weigert’s most notable personal characteristic was his excessive modesty. He was plagued by doubts about the value of his work and was never satisfied with what he had accomplished. Yet, he was indisputably successful in teaching advanced science students, both in the classroom and in the laboratory. His friend Ludwig Edinger wrote:
What attracted the many students from all over the world and what persuaded them to persevere in the small, poorly equipped rooms of the Frankfurt institute, which were in no way comparable to the proud university institutes, was the intimate relationship that existed between teacher and students. The door between his work room and the laboratory always stood open… A basic characteristic of his manner of working was never to stick too closely to details. Rather, he always sought to grasp pathological processes as biological processes… Weigert possessed an excellent philosophical training, and philosophical thinking governed his entire way of working. He disciplined himself to renounce any attempt to penetrate what could not be known and was made uneasy by metaphysical speculation… He always viewed the many facts he discovered as mere building stones. In his leisure he amused himself with mathematics.
According to the pathologist O. Lubarsch, Weigert was
…inwardly happy, a truly distinguished and good man, who viewed the weaknesses of those around him with the deep sense of humor of the philosopher and who reacted only mildly against those who wished to harm him. Nothing human was foreign to him, and after a day of hard work he sought relaxation in literature and society, amusing everyone with his warm-hearted humor and his witty conversation. His contact with Scandinavian students prompted him to learn their languages.
With his first major work on the eruption of smallpox on the skin (1874), Weigert opened a new area of research in pathological anatomy—the demonstration of the primary damage of cells and tissues by external influences. First he had to develop the histological techniques necessary to detect this process. With the aid of the improved microtome Weigert dissected pathological tissue into complete serial sections and devised a technique that enabled him to differentiate tissues sharply under the microscope. By 1871 he was able, by staining, to demonstrate the presence of bacteria in tissue sections. This advance was of the greatest importance for the subsequent work of Robert Koch. According to Ehrlich, Weigert’s monograph of 1874-1875 already contained “the points of view that guided his work for the rest of his life.” In this monograph he began to develop the theory of the “coagulation necrosis” (the term is due to Cohnheim) and to illustrate the reparative (bioplastic) processes of the supporting tissue. Before Roux he had developed also the concept that the cells of the organism are in equilibrium among themselves. Cells cannot disappear without the neighboring cells attempting to take over their place. If elements of the parenchyma disappear, then they are generally replaced by elements of the connective tissue group. Such substitute growth is at first excessive, but gradually a new equilibrium is established. Weigert later applied his theory of the secondary, reparative processes to the substitute growth of neuroglia following atrophy of the nervous parenchyma.
Weigert’s experiments on the staining of fibrin (1887) were also important for general pathology, since they exercised a lasting influence on the study of inflammation and on the theory of thrombosis. Weigert’s method for staining elastic fibers was also important (although published in 1898, the preliminary work on it began in 1884). In addition, Weigert conducted studies on the genesis of acute general miliarial tuberculosis (affecting the veins and thoracic duct). The studies are remarkable for pointing out its spread from a tubercular source, before the agent of the disease was even known.
Weigert’s most important work was in the field of neurohistology. After long preliminary investigation, he presented in 1884 the definitive method of staining medullary sheaths (myelin sheaths). This method enabled scientists to establish a reliable anatomy of the central nervous system. The number of works in this field multiplied within a few years of Weigert’s announcement. The research on comparative anatomy of the brain owes its existence to myelin staining; previously, the path of scarcely a single pathway in a lower vertebrate brain had really been established with certainty. Starting about 1886 the new results, which eliminated much speculation, found their way into the textbooks. Recalling this pioneering time, Edinger wrote (1906):
In the first years [of research] fetal brains, which contain only a few medullary sheaths and therefore provide particularly clear views, were a rich source of important facts. Myelin staining finally allowed us, in the middle of the 1880’s, to determine, for example, how the afferent nerves reach the brain. Their termination in the nuclei of the dorsal columns was known. From there, as has now been established, a crossed pathway leads to the thalamus. At that time, [however,] people proposed all kinds of uncertain paths leading from those nuclei through the olive into the cerebellum. One of the first works, begun in Weigert’s presence, was Lissauer’s study of the dorsal roots and the spinal cord, which is still absolutely valid. He and Weigert discovered in the first months that in the disease tabes dorsalis the dorsal (Clarke) columns degenerate.
Weigert sought to find evidence of the selective behavior of the supporting tissue of the nervous system in order to establish the system’s pathological histology. This effort led to his successful demonstration in 1887 of the existence of the neuroglia (His findings were not published until 1890.) He found, again, that the atrophy of the parenchyma is the primary process and results in the growth of the neuroglia as a secondary process. In this area, too, Weigert’s work has influenced neurohistological research up to the present, although his notion of the existence of neuroglia fibers “emancipated” from the cell and differentiable by staining did not remain unchallenged.
I. Original, Works. A chronological list of Weigert’s works is in R. Rieder (see below). See also J. Springer, ed., Gesammelte Abhandlungen von Carl Weigert, II (Berlin, 1906), which has biographical contributions by R. Rieder, K. Edinger, and P. Ehrlich.
Weigert’s works include “Über Bacterien in der Pockenhaut,” in Zentralblatt für die medizinischen Wissenschaften, 8 (1871), 609–611; Anatomische Beiträge zur Lehre von den Pocken, written with Max Cohn, 2 vols.: 1. Die Pockeneffloreszenz der äusseren Haut (Breslau, 1874), II.Über pockenähnliche Gebilde in parenchymatösen Organen und deren Beziehung zu Bakterienkolonien (Breslau, 1875); “Bismarckbraun als Färbemittel,” in Archiv für mikroskopische Anatomie und Entwicklungsmechanik, 15 (1878). 258–260; Die Brightsche Nierenerkrankung vom pathologisch-anatomischen Standpunkte, which is Sammlung klinischer Vorträge No. 162/63 (Leipzig, 1879) “Über Entzüundung (Inflammatio, Phlogosis),” in Eulenburgs Real Encyclopädie der gesamten Heilkunde (2nd ed., rev. and enl.), VI (1886), 325–358 (Weigert’s contribution was replaced by a corresponding article by Ernst Ziegler in the 3rd ed. ); “Zur Technik der mikroskopischen Bakterienuntersuchungen,” in Virchows Archiv für pathologische Anatomie und Physiologie und für klinische Medizin, 84 (1881), 275–315; “Über eine neue Untersuchungsmethode des Centralnervensystems,” in Zentralblatt für die medizinischen Wissenschaften, 20 (1882), 753–757, 772–774; “Thrombose,” in Eulenburgs Real-Encyclopädie der gesamten Heilkunde, 19 (1889), 638–648, also replaced by Ziegler in 1900; “Uber Schnittserien von Celloidinpräparaten des Centralnervensystems,” in Zentralblatt wissenschaftliche Mikroskopie2 (1885), 490–495; “Über eine neue Methods zur Färbung von Fibrin und von Microorganismen,” in Fortschritte der Medizin, 5 (1887), 228–232; “Zur pathologischen Histologie des Neurogliafasergerüstes,” in Zentralblatt für allgemeine Pathologie und pathologische Anatomie, 1 (1890), 729–737; “Beiträge zur Kenntnis der normalen menschlichen Neuroglia,” in Abhandlungen der Senckenbergischen Naturforschenden Gesellschaft, 19 (1895), fasc. 11; “Die histologische Technik des Centralnervensystems II.2. Die Markscheidenfärbung,” in Ergebnisse der Anatomie und Entwicklungsgeschichte,6 (1897), 1–25; “Über eine Methode zur Färbung elastischer Fasern,” in Zentralblatt für allgemeine Pathologie und pathologische Anatomie, 9 (1898), 289–292; and “Fibrinfärbung,” “Markscheiden der Nervenfasern,” “Neurogliafärbung,” in Paul Ehrlich, Rudolf Krause, Max Mosse, Heinrich Rosin, Carl Weigert, eds., Enzyklopädie der mikroskopischen Technik, 2nd ed. (Berlin-Vienna. 1910), I, 457–460; II, 231–238; 298–311.
II. Secondary Literature. On Weigert and his work, see L. Edinger, “Carl Weigerts Verdienste um die Neurologie,” in R. Rieder (see below), pp. 133–137; P. Ehrlich, “Weigerts Verdienste um die histologische Wissenschaft,” ibid., pp. 138–141; G. Herxheimer, “Carl Weigert,” in Zentralblatt für allgemeine Pathologie und pathologische Anatomie, 15 (1904), 657–662; W. Krücke, “Carl Weigert (1845-1904),” in W. Scholtz, 50 Jahre Neuropathologie in Deutschland (Stuttgart, 1961), 5–19; W. Krücke and H. Spatz, “Aus den Erinnerungen von Ludwig Edinger,” in Ludwig-Edinger-Gedenkschrift (Schrifter der Wissenschaftlichen Gesellschaft an der Johann Wolfgang Goethe-Universität Frankfurt am Main, 1st ser. (Wiesbaden, 1959), 19–23; L. Lichtheim, “Karl Weigert,” in Deutsche Zeitschrift für Nervenheilkunde27 (1904), 340–350.
See also O. Lubarsch, “Karl Weigert,” in Deutsche medizinische Wochenschrift, 30 (1904), 1318-1319; H. Morrison. “Carl Weigert,” in Annals of Medical History, 6 (1924), 163–177; R. Rieder, Carl Weigert und seine Bedeutung für die mediziniche Wissenschaft unserer Zeit, eine biographische Skizze (Berlin, 1906); A. Strümpell, “Zur Erinnerung an Carl Weigert,” in Deutsche medizinische Wochenschrift, 31 (1905), 230–232; and I. H. Talbott, “Carl Weigert (1845-1904),” in A Biographical History of Medicine (New York, 1970), 837–840.
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