30 MAMMALIA. 



may be deduced the nature of its food, and the consequent structure of its 

 digestive apparatus. On these characters are founded the division of mam- 

 miferous animals, into orders. 



The degree of perfection of the organs of touch, may be estimated accord- 

 ing to the number and mobility of the fingers, and according to the greater 

 or less depth with which their extremities are covered by the nail or hoof. 

 A hoof, for instance, which envelopes that part of the extremity which 

 would otherwise touch the ground, blunts the feeling, and renders the foot 

 incapable of seizing. The opposite extreme is, when only a single lamina 

 covers the upper surface of the end of the finger or toe, leaving to the other 

 all its sensibility. The nature of the food may be judged of by the appear- 

 ance of the molar teeth, to the form of which the articulation of the 

 jaws always corresponds. For cutting flesh, the teeth require to be edged 

 like a saw, and the jaws to close vertically, like scissors. To bruise grains 

 or roots, it is requisite that the molars have a flat crown ; that the jaws 

 should move horizontally, as well as vertically ; and that the teeth should 

 be composed of parts of unequal hardness, to give them the necessary 

 inequalities for this operation. The hoofed animals are all necessarily 

 herbivorous, and possess teeth of this description, since the structure of their 

 feet precludes them from seizing living prey. 



Animals with unguiculated toes or fingers, on the contrary, are suscepti- 

 ble of more variety in their modes of subsistence ; for, besides the form 

 of the molar teeth, they differ materially among themselves in the mobility 

 and delicacy of their toes or fingers. There is one characteristic, however, 

 which exercises a mighty influence on the dexterity of the animals possess- 

 ed of it, and which multiplies or greatly varies their modes of action. This 

 is the faculty of opposing a thumb to the other fingers, and of thus being 

 enabled to seize with facility the most minute objects. This opposition 

 of a fifth member to the other four, constitutes what is properly called the 

 hand, an organ which is carried to the highest degree of perfection in man, 

 in whom alone the anterior extremities are free. 



These various combinations strictly determine the nature of the diflTerent 

 mammiferous animals, and afford the characteristics from which orders 

 are formed. In the following pages, the Mammalia will be arranged under 

 the following orders : 



Order I. BIMANA, 

 " II. QUADKUMANA, 

 " III. CHEIROPTERA, 

 " JV. FER^, 



V. MARSUPIALIA, 



Order VI. GLIRES, 



VII. EDENTATA, 

 " VIII. PACHYDERMA, 

 IX. RUMINANTIA, 

 X. CETACEA. 



The total number of mammiferous animals described, according to Des- 

 marest, is about eight hundred and fifty, including, however, many species 

 imperfectly ascertained, and the fossil Mammalia ; of which, belonging to 

 the order Quadrumana, are one hundred forty-one, — Cheiroptera, ninety- 



