38 ANIMALIA VERTEBRATA. 
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 com- 
bined in order to produce a more perfect degree of intelli- 
gence, 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 de- 
signed in general for walking on the earth, but with vigorous 
and continued steps. ‘The forms of the articulations of their 
skeleton, are, consequently, strictly defined, which deter- 
mines all their motions with the most rigorous precision. 
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 cra- 
nium; the lower is formed of two pieces only, articulated by a 
projecting condyle to a fixed temporal bone; the neck con- 
sists of seven vertebr, 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 articu- 
lated, but simply suspended in the flesh, often resting on the 
sternum by means of an intermediate bone, called a clavicle. 
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