44 MAMMALIA. 



Division of the Mammalia into Orders. 



The variable characters which form essential differences among 

 the Mammalia are taken from the organs of touch, on which depends 

 their degree of ability or address, and from the organs of manduca- 

 tion, which determine the nature of their aliment, and are all closely 

 connected, not only with every thing relative to the function of di- 

 gestion, but also with a multitude of other differences relating even 

 to their intelligence. 



The degree of perfection of the organs of touch is estimated by 

 the number and the pliability of the fingers, and from the greater or 

 less extent to which their extremities are enveloped by the nail or 

 the hoof. 



A hoof which completely envelopes the end of the toe, blunts its 

 sensibility, and renders the foot incapable of seizing. 



The opposite extreme is when a nail, formed of one single lamina, 

 covers only one of the faces of the extremity of the finger, leaving 

 the other possessed of all its delicacy. 



The nature of the food is known by the grinders, to the form of 

 which the articulation of the jaws universally corresponds. 



To cut flesh, grinders are required as trenchant as a saw, and 

 jaws fitted like scissars, having no other motion than a vertical one. 



For bruising roots or grains, flat-crowned grinders are necessary, 

 and jaws that have a lateral motion; in order that inequalities may 

 always exist on the crown of these teeth, it is also requisite that 

 their substance be composed of parts of unequal hardness, so that 

 some may wear away faster than others. 



Hoofed animals are all necessarily herbivorous, and have flat- 

 crowned grinders, inasmuch as their feet preclude the possibility of 

 their seizing a living prey. 



Animals with unguiculated fingers were susceptible of more 

 variety; their food is of all kinds, and independently of the form of 

 their grinders, they differ greatly from each other in the pliability 

 and delicacy of their fingers. There is one character with respect 

 to this, which has immense influence on their dexterity, and greatly 

 multiplies its powers; it is the faculty of opposing the thumb to the 

 finger for the purpose of seizing minute objects, constituting what is 

 properly called a hand; a faculty which is carried to its highest per- 



