MAM?4ALIA. 31 



CLASS I. 



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 sensa- 

 tions, the most varied powers of motion, and in which all the different 

 qualities seem combined in order to produce a more perfect degree of in- 

 telligence, the one most fertile in resources, most susceptible of perfection, 

 and least the slave of instinct. 



As their quantity of respiration is moderate, they are designed in gene- 

 ral for walking on the earth, but with vigorous and continued steps. The 

 forms of the articulations of their skeleton are, consequently, strictly de- 

 fined, which determines all theiy motions with the most rigorous pre- 

 cision. 



Some of them, however, by means of limbs considerably elongated, and 

 extended membranes, raise themselves in the air; others have them so 

 shortened, that they can move with facility in water only, though this does 

 not deprive them of the general characters of the class. 



The upper jaw, in all of these animals, is fixed to the cranium ; the 

 lower is formed of two pieces only, articulated by a projecting condyle to 

 a fixed temporal bone : the neck consists of seven vertebrae, one single 

 species excepted, which has nine ; the anterior ribs are attached before, 

 by cartilage, to a sternum consisting of several vertical pieces ; their an- 

 terior extremity commences in a shoulder-blade that is not articulated, 

 but simply suspended in the flesh, often resting on the sternum by means 

 of an intermediate bone, called a clavicle. This extremity is continued by 

 an arm, a fore-arm, and a hand, the latter being composed of two ranges 

 of small bones, called the carpus, of another range called the metacarpus, 

 and of the fingers, each of which consists of two or three bones, termed 

 phalanges. 



With the exception of the cetacea, the first part of the posterior extre- 

 mity, in all animals of this class, is fixed to the spine, forming a girdle or 

 pelvis, which, in youth, consists of three pairs of bones — the ilium which 

 is attached to the spine, the pubis which forms the anterior part of the 

 girdle, and the ischium, the posterior. At the point of union of those 



