Among his most striking discoveries during his studies of the forms and movements of the Bacteria may be mentioned the nature of Zoogloea, the formation and germination of true spores—which he observed for the first 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 abiogenesis; as well as works on the bacteria of air and water, the significance of the bright sulphur granules in sulphur bacteria, and of the iron 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 powers, and the thoughtful (in every sense of the word) consideration of the work of others, and suggestive ideas attached to his principal papers, bear the same characteristics. If we overcome the always difficult task of bridging in imagination the interval between our present platform 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-killing fungi, microscopic analysis of water, &c. He was a foreign member of the Royal Society and of the Linnean Society, and received the gold medal of the latter in 1895. He died at Breslau on the 25th of June 1898.
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.)
COHN, GUSTAV (1840- ), German economist, was born on the 12th of December 1840 at Marienwerder, in West Prussia. He was educated at Berlin and Jena universities. In 1869 he obtained a post at the polytechnic in Riga, and in 1875 was elected a professor at the polytechnic at Zürich. In 1873 he went to England for a period of study, and as a result published his Untersuchungen über die englische Eisenbahnpolitik (Leipzig, 1874-1875). In 1884 he was appointed professor of political science at Göttingen. Cohn’s best-known works are System der Nationalökonomie (Stuttgart, 1885); Finanzwissenschaft (1889); Nationalökonomische Studien (1886), and Zur Geschichte und Politik des Verkehrswesens (1900).
COHOES, a city of Albany county, New York, U.S.A., about 9 m. N. of Albany, at the confluence of the Mohawk and Hudson rivers. Pop. (1890) 22,509; (1900) 23,910, of whom 7303 were foreign-born; (1910) 24,709. It is served by the New York Central & Hudson River and the Delaware & Hudson railways, by electric lines to Troy and Albany, and by the Erie and Champlain canals. It is primarily a manufacturing city. Hosiery and knit goods, cotton cloth, cotton batting, shoddy, underwear and shirts and collars are the principal products, but there are also extensive valve works and manufactories of pulp, paper and paper boxes, beer, pins and needles, tools and machinery, and sash, doors and blinds. The value of the factory products in 1905 was $10,289,822, of which $4,126,873, or 40.1%, was the value of hosiery and knit goods, Cohoes ranking fifth among the cities of the United States (of 20,000 inhabitants or more) in this industry, and showing a higher degree of specialization in it than any other city in the United States except Little Falls, N.Y. The Falls of the Mohawk, which furnish power for the majority of the manufacturing establishments, are 75 ft. high and 900 ft. broad, a large dam above the falls storing the water, which is conveyed through canals to the mills. Below the falls the river is crossed by two fine iron bridges. The city has a public library, a normal training school and the St Bernard’s (Roman Catholic) Academy. Cohoes was a part of the extensive manorial grant made to Killian Van Rensselaer in 1629 and it was probably settled very soon afterwards. It was incorporated as a village in 1848 and was chartered as a city in 1870.
COHORT (Lat. cohors), originally a place enclosed: in the Roman army, the name of a unit of infantry. The troops of the first grade, the legions, were divided into cohorts, of which there were ten in each legion: the cohort thus contained 600 men. Among the troops of the second grade (the auxilia) the cohorts were independent foot regiments 500 or 1000 strong, corresponding to the alae, which were similar regiments of cavalry; they were generally posted on the frontiers of the Empire in small forts of four to eight acres, each holding one cohort or ala. The special troops of Rome itself, the Praetorian Guard, the Urbanae Cohortes, and the Vigiles (fire brigade), were divided into cohorts (see further [Roman Army]). The phrase cohors praetoria or cohors amicorum was sometimes used, especially during the Roman republic, to denote the suite of the governor of a province; hence developed the Praetorian cohorts which formed the emperor’s bodyguard.
In biology, “cohort” is a term for a group of allied orders or families of plants or animals.