210 



ANIMAL BIOLOGY 



Hoofed Mammals. All the animals in this order walk 

 on the tips of their toes, which have been adapted to this 

 use by the claws having developed into hoofs. The order 

 is subdivided into the odd-toed (such as the horse with one 

 toe and the rhinoceros with three) and the even-toed (as 

 the ox with two toes and the pig with four). All the even- 

 toed forms except the pig and hippopotamus chew the cud 

 and are given the name of ruminants. 



Horse and Man Compared (Figs. 381, 399). To which 

 finger and toe on man's hand and foot does the toe of a 



horse's foot correspond ? 

 Has the horse kneecaps ? 

 Is its heel bone large or 

 small ? Is the fetlock on 

 toe, instep, or ankle ? 

 Does the part of a horse's 

 hind leg that is most elon- 

 gated correspond to the 

 thigh, calf, or foot in 

 man ? On the fore leg, 

 is the elongated part the 

 upper arm, forearm, or 

 hand ? Does the most 

 elongated part of the fore 

 foot correspond to the finger, palm, or wrist ? On the hind 

 foot is it toe, instep, or ankle ? Is the fetlock at the toe, 

 instep, or heel ? (Fig. 385.) Is the hock at the toe, in- 

 step, heel, or knee ? Order Why ? _ 



Specializations of the Mammals. The early mammals, 

 of which the present marsupials are believed to be typical, 

 had five toes provided with claws. They were not very 

 rapid in motion nor dangerous in fight, and probably ate 

 both animal and vegetable food. 



FIG. 381. Left leg of man, left hind leg 

 of dog and horse; homologous parts 

 lettered alike. 



