138 COMPAKISONS OF STRUCTUEE IN ANIMALS. 



In mammalia, the dorsal and lumbar vertebrae 

 are variable in number — the former, according 

 with the number of ribs on each side. In the 

 elephant and tapir, the dorsal vertebra? are 

 twenty in number; in the rhinoceros, nineteen; 

 in the dugong, eighteen ; in the horse, eighteen ; 

 in man, twelve; in the chimpanzee, thirteen; 

 in the porpoise, thirteen; and here we may- 

 observe that in the whale tribe, as respects the 

 rest of the vertebrae, no definite line of demarca- 

 tion separates between the lumbar, sacral, or 

 caudal. 



It wiU be interesting, here, to notice the 

 degree to which, in harmony with the limbs, 

 the character of the spinal colimm in mammaha 

 influences their style of locomotion. The fol- 

 lowing passage is from the fragment of a work 

 on the " Natural History of Quadrupeds," by 

 the present writer : " With respect to the 

 spinous processes of the lumbar vertebra, they 

 are less elongated than those of the dorsal, and 

 especially of the anterior dorsal vertebra ; and, 

 in general, their direction is opposite. The 

 spinous processes of the dorsal vertebra? point 

 obliquely backwards ; those of the lumbar 

 vertebrae obliquely forward ; at least, as a 

 general rule. Whence it would seem to foUow 



