MAMMALIA. 41 



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 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. 



As their quantity of respiration is moderate, they are designed 

 in general for walking on the earth; but with vigorous and continued 

 steps. The forms of the articulations of their skeleton are, conse- 

 quently, strictly defined, which determines all their motions with the 

 most rigorous precision. 



Some of them, however, by means of limbs considerably elon- 

 gated, 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 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 verte- 

 brae, one single species excepted which has nine; the anterior ribs 

 are attached before, by cartilage, to a sternum consisting of several 

 vertical pieces; their anterior 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 pha- 

 langes. 



With the exception of the Cetacea, the first part of the posterior 

 extremity, in all animals of this class, is fixed to the spine, forming 

 F , 



