58 ON THE PLACE OF MAN IN THE SCALE OF BEING. 



mobility of the fingers, and by the degree in which their extremities are en- 

 veloped, by the nail, claw, or hoof, that terminates them. When the fingers 

 are partly absent, or are consolidated together, and a hoof envelops all that 

 portion which touches the ground, it is obvious that the sensibility must be 

 blunted, whilst at the same time the extremity becomes incapable of prehen- 

 sion. The opposite extreme is where (as in Man) a thin nail covers only one 

 side of the extremity of the finger, leaving the other possessed of all its deli- 

 cacy ; where several such fingers exist, of which one can be opposed to the 

 rest, so as to render prehension more perfect, and to perform a great variety of 

 actions ; and where the plane of the whole hand can be turned in any posi- 

 tion, by the nature of its attachment to the forearm. Between these, there 

 are many intermediate gradations. By these characters, the viviparous Mam- 

 malia may be divided into the Unguiculated, which have separate fingers, 

 terminated by distinct nails or claws ; and the Ungitlated, in which the fingers 

 are more or less consolidated, and enclosed at their extremity in a hard hoof. 

 Hoofed animals are necessarily Herbivorous, inasmuch as the conformation of 

 their feet precludes the possibility of their seizing a living prey ; and they 

 have flat-crowned grinding teeth for triturating their food. The summits of 

 these teeth are usually not covered by a smooth coat of enamel, but present a 

 .series of elevations and depressions ; these are occasioned by the peculiar 

 structure of the teeth, which consist of alternating plates of enamel, ivory or 

 dentine, and cementum or crusta petrosa ; these are of three different degrees 

 of hardness ; and, as the softer portions will of course wear down first, the 

 harder remain as projecting ridges. In order to give effect to these, there is 

 usually a considerable power of lateral motion possessed by the lower jaw ; so 

 that a regular grinding action may be performed, which is favourable to the 

 complete reduction of the tough vegetable substances that serve as their food. 

 60. Animals with Unguiculated fingers are capable of more variety in the 

 character of their food. In some it is almost exclusively vegetable, as in the 

 Rodentia; and here the power of prehension possessed by the extremities is 

 small, the forearm not being so constructed as to be capable of the motions of 

 pronation and supination. In this order, the mouth is remarkably adapted for 

 grinding down hard vegetable substances, the molar teeth being furnished 

 with transverse ridges of enamel, and the jaws having a powerful movement 

 backwards and forwards.* In others, again, there is an almost exclusive adap- 

 tation to animal food. The toes are furnished with long and sharp claws ; 

 and the forefoot may be placed in a variety of positions, by the rotation of the 

 two bones composing the lower part of the leg. The grinding teeth are very 

 narrow, and are formed with sharp points and edgqs, so as to be adapted for 

 dividing animal flesh ; these are firmly set in short strong jaws, which are 

 fitted together like the blades of a pair of scissors, having no action but a verti- 

 cal one ; and the constant friction of the edges of the molar teeth against each 

 other, keeps them sharp.! In this group, too, we find the greatest develop- 

 ment of the canine teeth, which are commonly absent or but slightly developed 



* The action of trituration is chiefly performed by the external pteregoid muscles. 

 When these are in operation together, they draw the whole of the lower jaw forwards, so 

 as to make the lower teeth project beyond the upper; and the jaw being drawn back 

 again by the digastric muscles, a rapid alternate movement may be thus effected, such 

 as is seen in the Rodentia. When only the muscles of one side acts, the condyle of that 

 side is thrown forwards; and by the alternating operation of the two, aided by other 

 muscles, that rotatory motion is given which we see especially in Ruminating Quad- 

 rupeds. 



f In Carnivorous animals, the muscles which elevate the lower jaw attain a very high 

 degree of development. This is very remarkably seen in the internal pteregoid, which 

 in Man is of subordinate size and importance, but which is a very powerful muscle in 

 the Lion, Tiger, &c. 



