30 MAMMALIA. 



imperfectly ascertained and the fossil Mammalia ; of which be- 

 longing to the order Quadrumana are 141, Cheiroptera 97, 

 Ferae 176, Marsupialia 47, Rodentia 149, Edentata 24, 

 Pachydermata 55, Ruminantia 97, Cetacea 62. Of these 

 about 330 are frugivorous or herbivorous, 80 omnivorous, 1 50 

 insectivorous, and 240 carnivorous, in a greater or lesser de- 

 gree. The number of terrestrial species domesticated by Man 

 (but perhaps including all that are really useful) amount only 

 to thirteen. 



The essential characters of the Mammalia are taken from the 

 organs of touch and the organs of mastication. On the first 

 depend the power and dexterity of the animal ; and from the 

 second may be deduced the nature of its food, and the conse- 

 quent structure of its digestive apparatus. On these characters 

 are founded the division of mammiferous animals into Orders. 



The degree of perfection of the organs of touch may be es- 

 timated according to the number and mobility of the fingers, and 

 according to the greater or less depth with which their extremi- 

 ties 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 appearance 

 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 mo- 

 lars have a flat crown ; that the jaws should move horizontal- 

 ly as well as vertically ; and that the teeth should be com- 

 posed of parts of unequal hardness, to give them the necessary 

 inequalities for this operation. The hoofed animals are all ne- 

 cessarily 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 susceptible of more variety in their modes of subsistence ; 



3 



