STRUCTURE OF MAMMALS. 



559 



box of the monkey as compared with that of the lemur, and 

 of apes as compared with monkeys, while in man the brain 

 capacity is twice that of the highest apes. 



The different regions of the vertebral column are better 

 defined than in the birds and reptiles ; this is seen in the 

 cervical vertebras, the number of which is usually seven. 

 The exceptions to this rule are few, there being six in one 

 sloth (Clwlcepus], eight or nine in another sloth (Bradypus), 

 and six in the American manatee. Behind the cervical is 

 the dorsal region, consisting of from ten to twenty-four, 

 usually thirteen, vertebrae, and the lumbar region, which is 

 composed of from two to nine, usually six or seven, vertebrae, 

 and is marked off by the absence of movable ribs. The 



Fig. 484. Skull of the Lion. After Owen. 



shoulder-girdle is not solidly united to the dorsal vertebras, 

 but loosely attached by muscles and tendons. The pelvis 

 i.e., that portion called the ilium connects with a single, 

 sometimes two, rarely three, vertebras of the sacral region, 

 and the union of these vertebrae with one or more caudal 

 vertebras forms an assemblage of consolidated vertebras, called 

 the os sacrum, which in the sloths, or Edentates, comprises 

 eight or nine vertebras. The number of caudal vertebras 

 in the monkeys may amount to thirty, in the long-tailed 

 manis (Fig. 501) to forty, while in other mammals there may 

 be less than this number, there being four retained by man 

 and the larger apes, while in some bats there arc only 

 three. 



