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LEFT OREL 44 OREL, the capital of the province of the same name in Russia. It is on Oka river, about 240 miles S. of Moscow. There are several schools and a theologi- cal seminary. It is the seat of a bishop and contains several cathedrals. The chief manufactories are candles, oil, and flour. The city was founded in 1564. Pop. about 100,000. O'RELL, MAX. See Blouet, Paul. ORENBURG, a town of European Russia (Tartar-Bashkir Republic) on ' the Ural river; 727 miles E. S. E. of Moscow. Founded (1743) as a frontier fortress, it is now of importance for its commerce only; it imports cotton, silk stuffs, cattle, hides, etc., from Bokhara, Khiva, and Tashkend. Corn, metals, sugar, woven goods are the principal ex- ports. The town possesses an arsenal and two military schools. Pop. about 150,000. ORESTES, in Greek mythology, the son of Agamemnon and of Clytemnestra, the avenger of his father, by becoming the murderer of his mother. For this murder he is relentlessly pursued by the Eumenides or Furies, and only succeeds in appeasing these terrible goddesses by carrying out the instructions o' the Del- phian oracle to bring back the statue of Diana from Tauris to Argos. Married to Hermione, daughter of Menelaus, Orestes ruled over his paternal kingdom of Mycenae, and over Argos, upon the death of its king. Orestes is an impor- tant figure in the "Choephori" and the "Eumenides" of ^schylus, the "Electra" of Sophocles, and the "Orestes" and Scenes from the story of Orestes ap- pear in Greek decorative art. ORE AH, OORFA, or UREA (ancient Edessa) a fortified town of Asiatic Turkey, 78 miles S. W. of Diarbekr. It is well built, and has a considerable trade with North Syria and Mesopota- mia. It is supposed to be the site of the "Ur of the Chaldees," mentioned in Scripture. Pop. about 30,000, mostly Mohammedans. ORGAN, in anatomy, a member of an organized being through which its func- tions are executed. Thus the root, stem, and leaves of a plant are organs. In music, the most comprehensive and important of all wind instruments. Its history can be traced back to the earliest antiquity. Starting from a small collec- tion of pipes, perhaps even from a syrinx, it has gradually grown in size and complexity till, at the present day, one performer has complete control over many thousands of pipes. In its rudi- ORGANOTHERAPY mentary state, the wind was admitted to each pipe at the will of the player by means of a sliding strip of wood, which could be pulled in and out; this mechan- ism was the ancestor of our modern key- board. The next step was to have more than one series of pipes; strips of wood passing lengthwise under the mouths of each set enabled the player, by pulling a stop, to exercise a choice as to which he used. Afterward, as larger organs were constructed, the smaller were called "por- tative," because they could be carried about in processions, etc., and the large ones were called "positive," because they were fixtures. The essential principles of the construction of an organ were thus discovered, and it only remained to ex- pand the instruments. In modern in- struments, four, or sometimes even five, rows of keys are found, each represent- ing a distinct instrument; these are named after their use br characteristics; as, great organ, that used for grand ef- fects, the principal manual; choir organ, that used for the accompaniment of voices; solo organ, that containing stops for solo use; swell organ, pipes placed in a distant box, with shutters opening and closing like Venetian blinds, by means of which a crescendo can be made ; pedal organ, the pipes controlled by the pedals. Pipes range from 32 feet to % of an inch in length; they are divided into two great classes, flue and reed, names which need no explanation. The title of stops generally intimates their quality of tone, e. g., flute, violin, oboe, clarinet, trumpet, etc. In comparative anatomy and physi- ology, organ of Bojanus, a double organ with two bilaterally symmetrical halves, one on each side of the body, just below the pericardium. This organ performs the function of a kidney. ORGANIC CHEMISTRY, the chemis- try of the carbon compounds in which the hydrogen or nitrogen of the substance is directly united with carbon. ORGANIC RADICAL, a group of atoms containing one or more atoms of carbon, of which one or more bonds are unsatisfied. ORGANOTHERAPY. The branch of medical science using animal organs and their extracts for healing purposes. The use of animal tissues as medicines is as old almost as authentic history, and the belief in their eificacy prevailed amoiig al- most all races, though their early use was largely superstitious. But modern organotherapy may be said to have be- gun in the middle of the last century with the discovery of Brown-Sequard
 * Iphigenia in Tauris" of Euripides.