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Encyclopedia Britannica - Main :: CLI-COM |
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COHN, FERDINAND JULIUS (1828-1898) , German botanist, was born on the 24th of January 1828 at Breslau. He was educated at Breslau and Berlin, and in 1859 became extra- ordinary , and in 1871 ordinary , professor of botany at Breslau University. He had a remarkable career, owing to his Jewish origin. He was contemporary with N. Pringsheim, and worked with H. R. Goeppert, C. G. Nees von Esenbeck, C. G. Ehrenberg and Johannes Muller. At an early date he exhibited astonishing ability with the microscope, which he did much to improve, and his researches on cell-walls and the growth and contents of plant-cells soon attracted attention, especially as he made remarkable advances in the establishment
It is, however, in the introduction of the strict biological and philosophical analysis of the life-histories of the lower and most minute forms of life that Cohn's greatest achievements consist, for he applied to these organisms the principle that we can only know the phases of growth of microscopic plants by watching every stage of development under the microscope, just as we learn how different are the youthful and adult appearances of an oak or a fern by direct observation. The success with which he attempted and carried out the application of cultural and developmental methods on the Algae, Fungi and Bacteria can only be fully appreciated by those familiar with the minute size and elusive evolutions of these organisms, and with the limited appliances at Cohn's command. Nevertheless his account of the life-histories of Protococcus (1850), Stephanosphaera (1852), Volvox (1856 and 1875.), Hydrodictyon (1861), and Sphaeroplea (18551857) among the Algae have never been put aside. The first is a model of what a study in development should be; the last shares with G. Thuret's studies on Fucus and Pringsheim's on Vaucheria the merit of establishing the existence of a sexual process in Algae. Among the Fungi Cohn contributed important researches on Pilobolus (1851), Empusa (1855), Tarichium (1869), as well as valuable work on the nature of parasitism of Algae and Fungi. It is as the founder of bacteriology that Cohn's most striking claims to recognition will be established. He seems to have been always attracted particularly by curious problems of fermentation and coloration due to the most minute forms of life, as evinced by his papers on Monas prodigiosa (185o) and " trber blutahnliche Farbungen " (185o), on infusoria (1851 and 1852), on organisms in drinking-water (1853), "Die Wunder des Elutes " (1854), and had already published several works on insect
the journal, Beitrdge zur Biologie, which he then started (187o1871), and which has since become so renowned. Investigations on other branches of bacteriology soon followed, among which " Organismen der Pockenlymphe " (1872) and " Untersuchungen fiber Bacterien " (18721875) are most important, and laid the foundations of the new department of science which has now its own laboratories, literature and workers specially devoted to its extension in all directions. When it is remembered that Cohn brought out and helped R. Koch
paper on Anthrax (1876), the first clearly worked out case of a bacterial disease, the significance of his influence on bacteriology becomes apparent.Among his most striking discoveries during his studies of the forms and movements of the Bacteria may be mentioned the nature of Zoogloca, the formation and germination of true spores which he observed for the first time, and which he himself discovered in Bacillus subtilisand their resistance to high temperatures, and the bearing of this on the fallacious experiments supposed to support abiogenesis
bright sulphur granules in sulphur bacteria, and of the iron oxide
bear the same characteristics. If we overcome the always difficult task of bridging in imagination the interval between our present plat-form of knowledge and that on which bacteriologists stood in, say, 1870, we shall not undervalue the important contributions of Cohn to the overthrow of the then formidable bugbear known as the doctrine of " spontaneous generation," a dogma of despair calculated to impede progress as much in its day as that of " vitalism " did in other periods. Cohn had also clear perceptions of the important bearings of Mycology and Bacteriology in infective diseases, as shown by his studies in insect
Lists of his papers will be found in the Catalogue of Scientific Papers of the Royal Society, and in Ber. d. d. bot. Gesellsch., 1899, vol. xvii. p. (196). The latter also contains (p. (172)) a full memoir by F. Rosen. (H. M. W.) End of Article: COHN, FERDINAND JULIUS (1828-1898) If you wish, you can link directly to this article.
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