MAMMALS 



II 



form the staves to the barrel-shaped 

 body, supporting and protecting the 

 chest and vital organs. The tail is 

 very usefid in the horse and its 

 kind, being provided with long hairs, 

 hence a fly brush. In the whale 

 it supports a prodigious fin. In 

 the monkey it is developed into a 

 hand which enables the animal to 

 cling to trees. In many animals 

 the tail is a very expressive organ, 

 as in the dog. It wags when the 

 animal is pleased, stiffens when it 

 is enraged, while in the cat it be- 

 comes three or four times its usual 

 size. 



The Hmbs of the mammals, if we 

 compare them with those of other 

 animals, are particularly interesting. 

 As a rule, there are four, except in 

 the whales and manatees, in which 

 only the front limbs are well devel- 

 oped. In the horse the knee (k) is 

 found high up where it is least ex- 

 pected, the heel (/i) being at the end 

 of a very long foot upon which is the 

 hoof, which is in reality the toe nail 

 of a middle toe of three, two of 

 which have disappeared in the course 

 of time, one being represented by a spHnt (s, Fig. 2). 

 In the ruminants, as the ox, there is a remarkable modi- 



FiG. 2. — Fore Leg of 

 Horse. 



ca, carpus ; m, metacarpal 

 of the third digit ; s, 

 " splint bone," or rudi- 

 mentary metacarpal ; 

 I, first phalanx, or 

 " great pastern " ; 2, sec- 

 ond phalanx, or " small 

 pastern " ; 3, third pha- 

 lanx, or " coffin bone." 



