THE LIMBS. 169 



ent appearance. The backwardly projecting promi- 

 nence in the hock of the horse corresponds to the 

 heel of man, and the hinder surface of the horse's 

 limb, from the hock to the hoof, corresponds to the 

 plantar surf ace or " sole " of the foot of man. Man 

 is " plantigrade," the whole of the sole of the foot, 

 including the heel, being placed on the ground in 

 standing ; the horse is " unguligrade," walking only 

 on the hoof, incasing the tip (or last phalanx) of the 

 toe. Dogs and cats assume an intermediate position 

 (" digitigrade w ), for, although the metatarsal bones 

 and the heel are raised, not only the tips, but the 

 greater part of the plantar surface of the toes rests 

 on the ground. 



The sesamoid bones of the hind foot exactly re- 

 semble those of the fore foot. 



The Muscles of the Limbs. 



Muscles are the organs by which all the move- 

 ments of one part of the body in relation to any 

 other part are effected. They lie around the bones 

 and beneath the skin, giving the external form to the 

 animal, and constituting what is commonly called its 

 flesh. 



Muscular tissue is composed of a great number 

 of exceedingly minute parallel fibers of peculiar 

 structure, and it differs from all other tissue in pos- 



