402 



PRACTICAL ZOOLOGY 



Locomotion. — The habitat of an animal determines to a 

 large extent its method of locomotion. Whales swim about easily 

 in the water, but are helpless on land. Seals and walruses are 

 likewise excellent swimmers, but their flippers and heavy bodies 

 make locomotion on land very slow and awkward. Most of the 



spinal cord 



spinal column 



chest cavity 



diaphragm 



abdominal cavity 



Fig. 273. — Longitudinal section through the trunk of a human body (side 

 view). (From Peabody and Hunt.) 



mammals walk, run, or hop, but a few of them can sail through 

 the air for short distances, and the bats can actually fly. 



Internal Organs. — The body cavity in which the internal 

 organs lie is in mammals divided into two parts by a transverse 

 muscular partition called the diaphragm. The anterior portion 



