126 i V. I o. 



why in some of the polydactylous quadrupeds, such as wolves, 

 lions, dogs, and leopards, there are five digits on each fore-foot, 

 though there are only four on each hind one. For the fifth 

 digit of the foot corresponds to the fifth digit of the hand, 

 and like it is called the big one. It is true that in the smaller 

 polydactylous " quadrupeds the hind feet • also have each five 

 toes. But this is because these animals are creepers ; and the 

 mcreased number of nails serves to give them a tighter grip of 

 the ground, and so enables them to creep up steep places, or 

 even to run overhead, with greater facility .^^ 



In man between the arms, and in other animals between the' 

 fore legs, lies what is called the breast. This in man is broad, 

 as one might expect. For as the arms are set laterally on the 

 body, they offer no impediment to the expansion of this part. 

 But .in quadrupeds the breast is narrow, owing to the legs 

 having to be extended in a forward direction in progression and 

 locomotion. 



Owing to this narrowness the mammae of quadrupeds are 

 never placed on the breast. But in the human body there is 

 ample space in this part ; moreover the heart and neighbouring 

 organs require such protection as would be afforded by a fleshy 

 covering ; and for these reasons the mammae in man are placed 

 on the breast, side by side. In the male these mammae are 

 of a fleshy substance and are therefore of use in the way just 

 stated ; but, in the female, nature, in accordance ^^ with what 

 we say is her frequent practice, makes these organs minister 

 to an additional function, employing them as a store-place of 

 nutriment for the offspring. The human mammae are two in 

 number, in accordance with the division of the body into two 

 halves, a right and a left. They are somewhat firmer than they 

 would otherwise be, because the. ribs ^' in this region are joined 

 together ; and they form two distinct masses, because their 

 presence is in no wise burdensome.^* In other animals ^^ than 

 man, it is impossible for the mammae to be placed on the breast 

 between the fore legs, for they would interfere with locomotion ; 

 they are therefore disposed of otherwise, and in a variety of 

 ways. Thus in such animals as produce but few at a birth, 

 whether horned quadrupeds or those with solid hoofs, the mammae 

 are placed in the groins, and are two in. .number,^^ while in such 

 as produce litters, or such as are polydactylous, the dugs are 

 e88a. 



