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COHN, FERDINAND JULIUS (1828-1898)

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Originally appearing in Volume V06, Page 652 of the 1911 Encyclopedia Britannica.
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COHN, See also:FERDINAND See also:JULIUS (1828-1898) , See also:German botanist, was See also:born on the 24th of See also:January 1828 at See also:Breslau. He was educated at Breslau and See also:Berlin, and in 1859 became extra-See also:ordinary, and in 1871 ordinary, See also:professor of See also:botany at Breslau University. He had a remarkable career, owing to his Jewish origin. He was contemporary with N. See also:Pringsheim, and worked with H. R. Goeppert, C. G. Nees von Esenbeck, C. G. See also:Ehrenberg and Johannes See also:Muller. At an See also:early date he exhibited astonishing ability with the See also:microscope, which he did much to improve, and his researches on See also:cell-walls and the growth and contents of plant-cells soon attracted See also:attention, especially as he made remarkable advances in the See also:establishment of an improved cell-theory, discovered the See also:cilia in, and analysed the movements of, zoospores, and pointed out that the See also:protoplasm of the plant-cell and the sarcode of the zoologists were one and the same See also:physical vehicle of See also:life.

Although these early researches were especially on the See also:

Algae, in which See also:group he instituted marked reforms of the rigid See also:system due to F. T. Kutzing, Cohn had already displayed that activity in various departments which made him so famous as an all-See also:round naturalist, his attention at various times being turned to such varied subjects as Aldorovanda, torsion in trees, the nature of waterspouts, the effects of See also:lightning, See also:physiology of seeds, the proteid crystals in the See also:potato, which he discovered, the formation of travertin, the rotatoria, luminous See also:worms, &c. It is, however, in the introduction of the strict biological and philosophical See also:analysis of the life-histories of the See also:lower and most See also: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 See also:plants by watching every See also:stage of development under the microscope, just as we learn how different are the youthful and adult appearances of an See also:oak or a See also:fern by See also:direct observation. The success with which he attempted and carried out the application of cultural and developmental methods on the Algae, See also:Fungi and Bacteria can only be fully appreciated by those See also:familiar with the minute See also:size and elusive evolutions of these organisms, and with the limited appliances at Cohn's command. Nevertheless his See also:account of the life-histories of Protococcus (1850), Stephanosphaera (1852), Volvox (1856 and 1875.), Hydrodictyon (1861), and Sphaeroplea (1855–1857) among the Algae have never been put aside. The first is a See also:model of what a study in development should be; the last shares with G. See also:Thuret's studies on Fucus and Pringsheim's on Vaucheria the merit of establishing the existence of a sexual See also:process in Algae. Among the Fungi Cohn contributed important researches on Pilobolus (1851), Empusa (1855), Tarichium (1869), as well as valuable See also:work on the nature of See also:parasitism of Algae and Fungi. It is as the founder of See also:bacteriology that Cohn's most striking claims to recognition will be established. He seems to have been always attracted particularly by curious problems of See also: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 See also:infusoria (1851 and 1852), on organisms in drinking-See also:water (1853), "See also:Die Wunder See also:des Elutes " (1854), and had already published several See also:works on See also:insect epidemics (1869–187o) and on plant diseases, when his first specially bacteriological memoir (Crenothrix) appeared in the See also:journal, Beitrdge zur Biologie, which he then started (187o–1871), 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 " (1872–1875) are most important, and laid the See also:foundations of the new See also:department of See also:science which has now its own laboratories, literature and workers specially devoted to its See also:extension in all directions.

When it is remembered that Cohn brought out and helped R. See also:

Koch in See also:publishing his celebrated See also:paper on See also:Anthrax (1876), the first clearly worked out See also:case of a bacterial disease, the significance of his See also: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 See also:time, and which he himself discovered in Bacillus subtilis—and their resistance to high temperatures, and the bearing of this on the fallacious experiments supposed to support See also:abiogenesis; as well as works on the bacteria of See also:air and water, the significance of the See also:bright See also:sulphur granules in sulphur bacteria, and of the See also:iron See also:oxide deposited in the walls of Crenothrix. His discoveries in these and in other departments all stand forth as mementoes of his acute observation and reasoning See also:powers, and the thoughtful (in every sense of the word) See also:consideration of the work of others, and suggestive ideas attached to his See also:principal papers, See also:bear the same characteristics. If we overcome the always difficult task of bridging in See also:imagination the See also:interval between our See also:present plat-See also: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 See also:doctrine of " spontaneous See also:generation," a See also:dogma of despair calculated to impede progress as much in its See also:day as that of " vitalism " did in other periods. Cohn had also clear perceptions of the important See also:bearings of Mycology and Bacteriology in infective diseases, as shown by his studies in insect-killing fungi, microscopic analysis of water, &c. He was a See also:foreign member of the Royal Society and of the Linnean Society, and received the See also:gold See also:medal of the latter in 1895. He died at Breslau on the 25th of See also:June 1898. Lists of his papers will be found in the See also: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.

End of Article: COHN, FERDINAND JULIUS (1828-1898)

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