MAMIANI BELLA BOVERE. 756 Alinister to Alliens in 1801 and to Bern in 1805. He was also professor of history and philosophy at the University of Turin and editor of ha lilosolia dclle scuolc italiane. His works iii- '. .' .. • ,,o=-i. F>„i _; — «..«.„,..>(n della JOAMMALIA. elude: I'oesie (1857); Del rinTWvamcnto filoso/ia antica italiana (1834); Uialoght dt scienza (1848); Le confessioni di uii metafistco (18G5); D'un nuovo dirilto Europco (1859); I'sicologia di Kant (1877); La rcligione deW uiirnire (1879); and C'rilica dclle rivela;:iotn ( 1880). MAMILIA GENS. A plebeian gens at Uoiiie, orif;in:illv a family of Tusculum, which traced its origin to the dau^-hter of Telegoniis, the reputed founder of Tusculum. It comiirised three families, I.imetanus, Turrinus. and Vitulus. MAM.a;'A, Julia (a.d. -'.-235). A Koniau hulv, mother of the Emperor Alexander Scverus. A iiicce of Septiniius Scverus. she was born in Enicsa, Svria ; was a woman of hij;h principle, anil educated her son so well that be was a model of all virtues save generosity. ^Mama'a's greed ami paisimony roused to revolt the soldiers, who killed her anil her son. Ulpian was one of her advisers, and tradition makes her not unfriendly toward the Christians. MAMMA'LIA ( NeoLat. nom. pi., from Lat. mammali.i, relating to the breast, from 7nam)na, (jk. iidfiiiV mammf; breast). The highest class of vertebrates, which includes man, his domestic animals, and all others that suckle their young — the mammals. Mammals are warm-blooded; that is. the temperature of the body is kept aiijiroxi- niately at a li.cd ])oint, generally higher than that (if the surrounding medium. The fixed opti- mum temperature dilTers in difTerent mammals, but it is about 100° F. 1)EVEI.01'.IENT AND NoURI.SHMENT OF YoiXG. The most distinctive character of the mammalia is their mode of development and of nourishment during the earliest period of life. Excepting only tlie lowest forms ( I'rototheria ) , all are brought into the world alive, not merely by the retention and batching of the egg within the oviduct, but by the formation of a new connection between the embryo and its mother. The minute ovum (see Emurvolooy, Human) on reaching the uterus (or womb) connects itself by a set of root-like tufts of vessels with the maternal ves- sels in the wall of the uterus. These tufts form an organ called 'placenta.' by which the embryo absorbs nutriment from the mother's blood, and which conveys back to the mother's circulation for excretion by her the waste products of meta- bolism. All mammals nourish their young (which at first are unable to digest any other sort of food) u])on milk (q.v.). a richly nutritious fluid se- creted by the mother's body in 'mammary' glands, which become greatly developed in the female during the periods of gestation and lactation; and. as this is found in no other class, it is the character by which the entire group is most posi- tively defined, and from which it derives its name. The mammary glands exist in both sexes, but, except in very rare cases, it is only in the female that they secrete milk. Their number is never less than two. and. when more, is generally nearly proportional to that of the young produced at each birth. That there is direct connection beween the number of young and the number iif teats has recently been shown in the case of ewes which have been bred to throw two, three, or more young at a birth. In such cases the number of teats has increased proportionately. Their position varies, being determined in each case by convenience of approach by the suckling young. In the whales, where prolonged sucking would be dilhcult on account of their aquatic life, the duets of the glands are dilated to form a reser voir from which the milk is ejected into the mouth of the young by a compressor muscle of the mother, "in the Prototheria (q.v.) the mam- mary glands have no teats, but the milk simply oozes out through numerous pores. In the marsupials the teats are well developed, but the glands are provided with special muscles by which milk is forced into the mouth of the ex- tremely rudimentary young in the mammary pouch.' The skin in the mammalia produces a covering of hair (q.v.), which is a peculiar char- acteristic of this group, .so that it would be a sullicient definition of a mammal to say that it is an animal producing hair. In some, how- ever, it is modified into bristles, scales, and other unusual forms, or it may be almost wholly ab- sent, as in whales. The general structure is typified by that of man, and is abundantly described elsewhere, so that no more need be said here than a few words in reference to the cranium. Among the most characteristic points in the mammalian skull it may be mentioni'il generally ( 1 ) that the lower jaw articulates directly with the skull, there being no intervening tympanic bone, such as oc- curs in the other vertebrates; and (2) that the occipital bone of the skull articulates with the first vertebra by two condyles, one on ether side of the occipital foramen, as in amphibians, in- stead of by a single condyle, as in the reptiles and birds. In proportion as a mammal is re- mote in relationship from man, we find that the cranium is diminished; that the face is prolonged by extension of the jaws and nasal cavities; that tiie orbits are directed outward, and are less distinct from the temporal fossa-; and that the occii)ital foramen and condyles are placed toward the posterior part of the skull, instead of occupy- ing the middle of its inferior surface, as in man. For further information as to anatomy and physiology, see the articles Skeleton ; Teeth ; and those upon the various organs and functions of the human body, with the articles on com- parative anatomy accompanying them ; also articles upon the various groups of mammals, as Carnivora; Ruminant; Elephant; and the like. Jlalnnials are very generally distributed over the surface of the globe, and the details in re- gard to the distribution of the various sub- classes and order.s are extremely interesting. Among some of the most important facts may be mentioned the absence of mammals from New Zealand and oceanic islands ; the restriction of monotremes and all marsupials (except the American opossum) to Australasia; and the pe- culiar mammalian fauna of Madagascar. See Distribution op Animals. With respect to their natural history, the part they play in the interrelations of the living world, and their economic service to man, a large volume might easily be written. Mammals are found under all possible conditions of life; they inhabit the air, trees, surface of the earth and subsoil, and fresh and salt water, from the equator to the poles. They thus exhibit an extra-
