DIAPHRAGM. 206 BIAS. and several simillcr o|U'ninj;s in I lie iliaphragin. Tlirou-rh the luriiier |mss llie alxioiiiiiial aorta, the vena azjfros major, tlie thoracic Jnct, the a-sopliajnis. pneuuiogastric nerves, and vena cava. The diaphra^'ni is convex ahove and is in relation with the pleunr of the luiip« and pericardium; while its concave dome is invested by the peri- toneal lining of the ahdomen. Durin;r respira- tion the hei<.'!it of the diaphragm constantly changes; it descends during inspiration and thus increases the capacity of the thora.x, so that air rushes in to till the vacuum formed. This con- traction of the diaphragm also raises the ribs and widens the chest laterally. In expiration the iliaphragm returns to its former positi<m. The descent of the diaphragm encroaches u])on the abdomen and lessens its capacity. In all expul- sive acts the diaphragm by its contractions gives increased power to tlie effort and is accordingly an important factor in sneezing, coughing, laugh- ing, and crying, as well as in the expulsion of urine and fa-ces. Hiccoughing is due to spas- modic contraction of the diapTiragiu. DIAPHRAGM. A partition with a hole in it. enii)loyed. not only in landscape and portrait lenses for photography, but also in telescopes, microscopes, and other optical instruments, for the purpose of cutting off the supcrlluous rays of light, and (iroducing greater intensity or sharpness of the image by decreasing the amount of spherical alierration. (See .liF.UK.Tiox, Si'iiERiCAL. ) The diaphragm only permits those rays to pass which go through the central portion of the lens. The aberration of these rays is much less than those which pass through the lens nearer its circumference. DIARBEKIR, de iir'br k.-r'. or DIARBEKR, dear-bek'r. A town of Asiatic Turkey, capital of a vilayet of the same name, situated near the right bank of the Tigris, from which it is sepa- rated by extensive gardens (Map: Turkey in Asia, .J 4). It is circular in shape, and is sur- rounded by high, strong walls, flanked with towers and pierced by four gates. The streets are dirty, and the houses for the most part are built of rough stone., plastered with a compo- sition of mud and straw, but some of the better class are of black basalt. It has numerous hand- some mosques, khans, and bazaars, and several Christian churches. Extensive manufactures of silk, cotton, and other goods were at one time carried on at Diarbekir, and the trade between Aleppo and Hajrdad contributed greatly to the importance of the town, but the manufactures and trade have now greatly declined. Its present manufactures consist of red and yellow morocco, silk, and eop|)er ware. Diarbekir occupies the site of the ancient Amida, which was a place of importance in the reign of Constantius, by whom it was strengthened and enlarged. In this reign it was taken l>y the Persians, from whom it was ngain cajitured by the Romans; but in .502 the Persians once more became masters. After many vicissitudes it passed into the hands of Siiltan Selini in l.ll.n. Its population is estimated at 47.000, chiefly Mohammedans. DIARRHCEA (Lat. ilinrrhrrn. from fik. AiA'pfwin, iliiinliiila, a flowing through, from iiip^eiii, tliarrhcin. to flow through, from (tid, 'lia, through -4- !>eiv, rhein, to flow). A sjmp- tom of many diseases, consisting in frequent fluid discharges from the bowels. It occurs in catarrhal or inflammatory diseases of the various parts of the bowels, as enteritis. colili>. and duo- denitis, in cholera, typhoid fever, Itright's dis- ease, dysentery, and tubi'nulosis. ll is often a temporary aflVction, due to an effort of nature to remove poisonous or indigestible substances from the intestine. It follows the use of ]uirgativc medicines, as is intended. It sometimes occurs in wasting dise;ises, from the relaxed condition of the blood-vessels of the intestines, whereby the water of the blood soaks through and escaiies with the f;rces. Pain, some >veakness, an<l sore- ness accompany it in most cases. The treatment nuist be directed, as usual, to removing the cause. If the diarrluea is caused by indigestiMes. a cathartic like castor-oil or rhuliarb should be used, and very little simple focnl should be given for a day afterwards. In other cases carminative and astringent drugs are used, such as ginger, catechu, cardamom, bismuth, chalk, or boiled Hour. Opium, lead, iron, capsicum, and cam- plior are sometimes prescribed. Before using drugs it is, however, necessary to determine, in all but simple eases, whether the diarrluea is ben- eficial and therefore should not be cheeked. .See ClIOUCB., DIARY (Lat. diariinii, from dies, day). A word which means simply a daily record. It does not, however, comprehend every sort of daily rec- ord, but only such as have reference to the writer ]>ersonally. In it the man of letters inscribes the daily results of observation, reading, or thought; to the business man it serves the purpose of an order or day book; while the physician finds it indispensable as a register of engagements. The usual diar)- is a book with a separate blank s|)ace for each day in the year, these spaces varying in size and form, as the particular bent or profession of the diarist may rciuler necessar}'. It usually contains some general infi>rmation, especially a calendar. Some men. however, use any convenient blank book. The tireeks had the diary, which they called the r/ihcnirris (mean- ing "of the day'). This word in its plural form, ciilicmcriilcs. has been adopted by sonu> .scholars; it is the name that Casaubon gave to the records of his daily studies. The word joiiniiil is also in use; we have, for example, the .luiiriiiil of Sir Walter h!roll. Diaries have often furnished the historian with invaluable material, supplying the absence of jiublic records, and furnishing minute and graphic details of the social condition and the secret springs of public events that are not to be looked for in more formal records. Per- haps the most notable in this respect are the diaries of Evelyn and Pepys (q.v.). DIAS, de'As. Bartiioi.omei- (?-1.500). A Por- tuguese navigator and the discoverer of the Cape of Good Hope. He came of a family of famous sailors. .ToAO DiAS was nsscK'iated with Oil Eannes on the voyage of 14.'?4. when Cape Boja- Jor was first do«ibled. and DiMZ Dias was the discoverer of Cape Verde in 1445. PARTHOi-OMEt' Dias de Xovae.s ntade a voyage to (iuinea for ivory ami slaves in 147S. and in 14S1 he was in command of a vessel sailing to the (!old Coast. Dias was a cavalier of the King's hovisehidd and superintendent of the royal warehouses when, in Oetolier. 14SI>. King John of Portugal selected him to bear a message to Prester .Tohn by sailing around .friea. After several months of prep- aration Dias sailed for the south in the early
