ORGANIZATION 241 



presented by a dog, the most obvious fact is his power 

 of moving from place to place, a power produced by 

 the interplay of muscles and bones. We observe, also, 

 that his motions are neither mechanical nor irregular ; 

 there is method in his movement. He has the power 

 of willing, seeing, hearing, feeling, etc. ; and these 

 functions are accomplished by a delicate apparatus of 

 nerves. 



But the dog does not exhibit perpetual motion. 

 Sooner or later he becomes exhausted, and rest is 

 necessary. Sleep gives only temporary relief. In 

 every exercise of the muscles and nerves there is a 

 consumption or waste of their substance. The blood 

 restores the organs, but in time the blood itself needs 

 renewal. If not renewed, the animal becomes emaci- 

 ated, for the whale body is laid under contribution to 

 furnish a supply. Hence the feelings of hunger and 

 thirst, impelling the creature to seek food. Only this 

 will maintain the balance between waste and repair. 

 We notice, therefore, an entirely different set of func- 

 tions, involving, however, the use of motion and will. 

 The dog seizes a piece of meat, grinds it between his 

 teeth and swallows it. It passes into the stomach, 

 'where it is digested, and then into the intestine, 

 where it is further changed; there the nourishing 

 part is absorbed, and carried to the heart, which 

 propels it through tubes, called blood vessels, all 

 over the body. In this process of digestion, certain 

 fluids are required, as saliva, gastric juice, and bile : 

 these are secreted by special organs, called glands. 

 Moreover, since not all the food eaten is fitted to make 

 blood, and as the blood itself, in going around the body, 

 acts like a scavenger, picking up worn-out particles, we 

 have another function, that of excretion, or removal of 

 useless matter from the system^ The kidneys and lungs 

 DODGE'S GEN. ZOOL. 16 



