MAM 



[274] 



MAM 



called also mineral pitch, from its 

 resemblance to pitch. Colour black 

 or dark brown. Specific gravity 

 from 1-45 to 2-07. 



MA'MMA. (mamma, Lat.) The breast. 



MA'MMAL. An animal belonging to 

 the class mammalia. 



MAMMA'LIA. (from mamma, Lat. the 

 breast.) The highest class of ani- 

 mals is that which comprehends 

 man, and animals, which, like 

 man, possess a viviparous mode of 

 generation. The class mammalia 

 is divided by some authors on 

 natural history into two principal 

 sections, namely, Placentalia and 

 Marsupialia, or Implacentalia. 

 These animals have a heart con- 

 sisting of four cavities, two auricles 

 and two ventricles ; they have hot 

 and red blood. Their most essen- 

 tial character is that of their being 

 viviparous, and suckling their 

 young on milk, secreted in mam- 

 mary glands, which open by ducts 

 or teats, and they are thence called 

 Mammalia. The mammalia are 

 placed at the head of the animal 

 kingdom, not only because it is the 

 class to which man himself belongs, 

 but also because it is that which 

 enjoys the most numerous faculties, 

 the most delicate sensations, the 

 most varied powers of motion, and 

 in which all the different qualities 

 seem combined in order to produce 

 a more perfect degree of intelligence 

 the one most fertile in resources, 

 most susceptible of perfection, and 

 least the slave of instinct. The 

 muscular system and the living 

 movements of mammalia are more 

 varied than in any other vertebrated 

 class, for some are organized to 

 plough the deep, or to clamber on 

 the rocky coasts ; some to burrow 

 in the e'arth, or to bound over the 

 plains; some to gambol on lofty 

 trees or cliffs, or to wing their way 

 through the air, and these different 

 conditions affect more especially the 

 organs of motion. The bones of 



all the mammalia are nearly of the 

 same colour and general appearance 

 as those of man ; they are covered 

 with a periosteum, and contain 

 marrow, which in the whale tribe 

 is fluid. The skeleton of mammalia 

 is divided into head, trunk, and ex- 

 tremities. Next to man, the ape 

 tribe is found to have the largest 

 skull in proportion to the face, but, 

 even in the ape, it is found to be 

 small when compared with that of 

 man. The facial angle, which in 

 the adult European is about 85, is 

 in the ourang outang 67, gradually 

 descending in some of the monkeys 

 as low as 30, till among the other 

 genera of quadrupeds it does not 

 sometimes exceed 20. It may be 

 mentioned, that the cerebral system 

 not only exhibits an ascending series 

 of advances, from the lowest fish up 

 to the highest mammal, but that, 

 in the highest mammal, a parallel 

 series of advances obtains, from the 

 fish-like condition of the brain, at 

 an early fa3tal age, up to its com- 

 plete development. Among the 

 vertebrate classes, the brain is the 

 most completely developed in the 

 mammalia, and, among the mam- 

 malia, in man. The characters 

 which serve to distinguish the brain 

 of mammalia from that of other 

 vertebrated animals consists, ac- 

 cording to Cuvier, in the existence 

 of a corpus callosum, a great comis- 

 sure, fornix, cornu ammonis, and 

 tuber annulare ; in the situation of 

 the tubercula quadrigemina; in the 

 absence of ventricles, or cavities, in 

 the thalami nervorum opticorum; 

 in the position of the above men- 

 tioned thalami within the hemis- 

 pheres, and in the alternate lines of 

 grey and white within the corpora 

 striata. The young of mammalia 

 are nourished for some time after 

 birth by milk, a fluid peculiar to 

 animals of this class, which is pro- 

 duced by the mammas at the time 

 of parturition, and remains as long 



