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* OSLEB. 133 OSMOSIS. Bondhead, Ontario, was educated at Trinity Uni- versity, Toronto, and at the medical faculty of ilcGill University, Montreal, where he graduated in 1S72. He also studied at University College, f London, England, and at Berlin and Vienna. In 1874 he returned to Canada and was apjjointed professor of phj-siolog}' and patliology in iletiill University; ten years afterwards lie was called to the chair of clinical medicine in the University of Pennsylvania. In ISS'J he was made professor of the principles and practice of medicine in Johns Hopkins University and chief physician to the Johns Hopkins Hospital. His chief publi- cations include: Clinical Xotes on SinulliJox (1876); Histology Notes (1882); Cerebral Pal- sies of Children (1880) ; and The Principles and Practice of Medicine (18!I2 et seq.). OSMAN, os-miin'. Founder of the Ottoman Enijiirc. .See Otiiman. OSMAN DIGNA, dig'na (e.lSSfi— ). A fol- lower of the ilahdi in the Sudan. He was born, according to some, at Suakin, while others give his birthplace as Rouen, France, and his father as a Scotchman named Xisbet. Acconling to this latter account, the family moved to Alexandria, in 1849, where the father soon died, and the widow married a Turk named Osman, who adopt- ed young Nisbet and called him Osman Ali. They went to Suakin and engaged in the slave trade, Osman continuing the traffic after the death of his stepfather. His business of slave-selling being bioken up by the English, he took part in the revolt of Arabi Pasha (q.v.), and after the failure of that movement he attached himself to the cause of the Ilahdi. About this time he received the name Digna because of the full- ness of his beard; also the title of the "Emir of the Dervishes of God.' He maintained himself at the head of a powerful army around Suakin and inflicted a severe defeat on I5aker Pasha near Tokar, southeast of that place, on February 4, 1884. Immediately after this victory, however, lie was defeated by General Graham near Tokar and at Tamanieb. As the !Mahdi's ablest gen- eral he was largely responsible for the fate of CJordon and the loss of the Sudan to the Eng- lish. In December. 1888, he suffered a bloody reverse at the hands of General CJrenfell, l)ut nevertheless continued his raiding expeditions in the Sudan. In 1890 he fought in the last cam- paign of the Jlahdist forces, whose strength had Ijeen broken the previous year at Omdurman. On January 19, 1000, he was captured near Tokar and sent a prisoner to Rosetta. OSMANIE, cjs-ma'ne-a. Order of. A Turkish order conferred for conspicuous service to the State. It was established by Abd-ul-Aziz on his accession to the throne in 1861, and has four classes. The decoration is a green-enameled gold star with six points, suspended by the star and crescent from a green ribbon with red bands. In the centre of the star is a crescent on a red back- ground. OSMAN'LIS. See Ti-kket. OSMAN NURI PASHA, os-miin' noo'rS p4- shii' (1837-1000). A Turkish general, called Ghazi (the victorious). He was liorn at Amasia, in .Asia !Minor. He was educated for the army at the Turkish military academy, became a sub- altern officer in 18.54. and fought in the Crimean War. He took part in the suppression of the rebellion of the Druses (1860), and in that of the Cretan insurrection of 1866-68. He was made a general of brigade in 1874, and in the follow- ing year a general of division. When Servia made war upon the Ottoman Empire in 1876, lie was put in command of a corps of 35,000 men at Widin, and his successes won him the rank of marslial. In July, 1877, he took up a strongly fortified position at Plevna, tlius arrest- ing the advance of the Russians. He inflicted a severe defeat upon them on July 30th, and successfully withstood a desperate assault made by them and their Rumanian allies on Septera- lier 11th. He held his position until his supplies failed him, and at last on December lOlh made a gallant effort to break through the enemies' lines. Overpowered bj- superior numbers, he was forced to surrender. He was taken to Russia as a prisoner of war, but after the Treaty of San Stefano (1878) returned to Constantinople and be- came commander-in-chief of the Imperial Guard. He was Minister of War, 1878-85, and Grand Marshal of the Palace till his death, which oc- curred at Constantinople, April 4, 1900. Consult hevaux, Ghazi Osman Pacha (Paris, 1891 ). See Rus.so-TuRKisH War. OSMIUM (Xeo-Lat., from Gk. 6<rfi-n, osmC; dd/i-ri, odme, odor, from Sfeiv, ozein, to smell). A metallic element discovered by Tennant in 1803. It is one of the phtinuin metals, and is found native allo-ed with rliodium, ruthenium, and palladium. When o.sni iridium, which is found as a hard, cr.ystalline substance (insoluble in aqua regia ) in platinum ores, is heated to a white heat in porcelain tubes in a current of air, the volatile oxide of osmium (OsOj readily sublimes over. Metallic osmium may be obtained from the oxide by reducing the latter with hydro- gen, carbonic oxide, or carlron. Osmium (symliol. Os; atomic weight, 191) is a lustrous, Ijlue-wliite metal with a specific gravity varying between 20 and 22. .5. It is extremely difficult to fuse, much more so than platinum and iridium. Its compounds with oxygen include a monoxide (OsO), a sesquioxide (OsX)^), a diox- ide (OsO,). and the tetroxide (OsO,) mentioned above. The tetroxide is the only one of the oxides that is volatile. Osniic acid, H-OsO,. has been olitained in the free state by the decomposition of its potassium salt (potassium osmate, K,Os- 0,) with water and precipitating with alcohol in a current of hydrogen. OSMO'SIS (Neo-Lat., from Gk. dia/ws, osmos, impulsion, from liSeri/, olhcin, to push). This phenomenon, which is discussed in its funda- mental form and from the pliysical point of view under SOLUTIOX, plays an important jiart in plant physiologv'. The plant cell, consisting of a mass of protoplasm, surrounded by a somewhat tough but flexible and elastic membrane, the cell wall, and inclosing a watery fluid, the cell sap. is an appropriate mechanism for an cft'ectivc dis- play of osmotic phenomena, which are fundamen- tal to three important functions: (1) turgor (q.v.). (2) absorption and transfer of water. (3) ab.sorption and transfer of dissolved substances. (See AiisoHi'Tio.N ix Pi,axt.s.) The general prin- ciples set forth under Solltiox may be summar- ized with resiject to plants as follows: (a) Dis- solved substances diffu.se to the limits of the sol- vent and exert an osmotic pressure comparable to gas pressure ami manifesting the same laws.