MAYIANI, Count TERENZIO, an Italian philosopher, statesman, and writer, b. in 1801, at Pesaro. Having taken a prominent part in the futile revolutionary outbreak which accompanied the accession of Gregory XVI., Mamiani was compelled to seek safety in flight, and repaired to Paris, from whence he promoted with energy the revo lutionary tendencies of his country. In 1846, on the accession of Pius IX., he declined the proffered papal amnesty, as long as its acceptance involved a disavowal of his former political principles; but on its being unconditionally granted, he availed himself of it, and even formed part of the papal ministry on the promulgation of the constitution. The inconsistent policy of the pope having compelled him to resign his post, he with drew to Turin, where he founded, with Gioherti, a society for promoting the union of Italians. On the flight of Pius IX. from Rome to Gaeta, he re-entered the political arena, and was for a short period foreign minister in the revolutionary cabinet of Galetti. On the fall of Rome he retired to Genoa; in 1856 lie was returned member of the Sardinian parliament, and in 1860 entered Cavour's ministry as minister of instruction. He was appointed ambassador to Greece in 1861, to Switzerland in 1865. His chief works are: Del Rinnovanzento della Filoso,fia antica Balkna (1836); Poeti dell' eta Media (1842); Dell Ontologia e del Metodo ; Principi della Filosofia del Diritto, and a number of treatises on various subjects. In 1870 he became editor of a new quarterly review, FiTosofta della Scuole Italiane.
IIAMMA'LlA (Lat. mamma, the breast), the highest class of the animal sub-kingdom rertebrata (q.v.). This class includes man and all the animals which resemble him in the most important points of their organization; and it is naturally placed at the head of the animal kingdom because (independently of man being a member of it) it contains the animals which manifest the highest degree of intelligenc,e, and which possess the most complex organization.
The most distinctive character of the mammalia is their mode of development and of nourishment during the earliest period of life. They are all brought into the world alive (viviparous), not merely, as in certain (ovo-viviparous) reptiles and fishes, by the reten tion and hatching of the egg within the oviduct, but by the formation of a new connec tion between the embryo and its mother, while the fonner lies within the maternal cavities, so that provision is made for its development before birth, not, as in birds, etc.,
by the large yelk (see DEVELOPMENT OF THE EMBRYO, but by a constant supply of nutri ment direct from the maternal blood. In mammals, the ovuin on quitting the ovary is of extremely minute size, and the materials of the yelk only serve to support the embryo during its very earliest period. After undergoing certain changes in the passage through the Fallopian tube or oviduct, which it is unnecessary here to notice, the ovum reaches the uterus or womb, and connects itself by a set of root-like tufts of vessels with the maternal vessels. These tufts absorb from the mother's blood the ingredients necessary for the support of the embryo, while they convey back to it the effete particles of the embryonic tissues. Through this organ, which simultaneously increases in size with the embryo, and is named the placenta, the young animal, except in the lowest orders of the class—viz., the marsupialia (q.v.) and the monotremata (q.v.)--derives its nutriment dur ing the whole period of gestation (q.v.); while in the two orders just named no vascular connection of the ovum with the uterus of the mother is formed, the ovum being simply retained for a time within the uterus, and the requisite nourishment for the development of the young animal being obtained by absorption through the membranes of the ovum. This remarkable difference in the development of the mammalian embryo has given rise to a division of this cla.ss into two great sections or sub-classes—the placental and the impla,cental (or aplacental) inammals. In both sub-classes we find the same provision for nourishing the animal during the period immediately succeeding its birth—viz., the milk (q.v.), a fluid secreted by peculiar glands, called the mammary glands, which become greatly developed in the female dunng 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 positively defined, and from which it derives its name.