14 THE HOESE. 



To understand one of the principal distinctions 

 between these two forms, it must be premised by 

 way of explanation that the number of digits (a con- 

 venient common term to express either fingers or 

 toes, whether of the fore or hind foot) in mammals 

 never exceeds five on each limb. For convenience 

 of description, they are designated numerically from 

 the inner side of the limb I., II., III., IV. and V. 

 (Fig. 1, p. 15) the pollex (thumb) and hallux (great toe) 

 being the first of the fore and hind limbs respect- 

 ively, and the third is the middle of the complete 

 series. When the number falls short of five, it is 

 always easy to determine, by their relations to the 

 bones of the wrist or ankle, which of the typical 

 series are present and which are missing. 



In the Artiodactyles the third and fourth digits 

 of both feet are almost equally developed, and flat- 

 tened on their inner or contiguous surfaces, so that 

 each is not symmetrical in itself, but when the two 

 are placed together they form a figure symmetrically 

 disposed to a line drawn between them, and consti- 

 tute the erroneously called " cloven hoof" of the Ru- 

 minants, which is really not one, but the two hoofs 

 of distinct toes. These two digits are always pres- 

 ent and well developed; the second and fifth may 

 be present in varying degrees of development, or 

 may be entirely absent ; the first is not present in 



