130 



ANIMAL BIOLOGY 



secures food. But whatever a fish feeds upon, and however 

 it secures its food, it is evident that plants and other animals 

 must furnish the food substance required to make living 

 matter, and so provide for growth and repair of the cells, 

 and also furnish the fuel needed to develop the energy nec- 

 essary for the various activities of the fish. 



98. Digestion and digestive organs. — We have seen in 

 plants (P. B., 63, 70, 74) that digestion may take place in 

 any living cell where food is stored or manufactured. Hence 

 plants have no special part devoted to digestion. In fishes 

 however, it is quite different, since a portion of the body, 

 known as a digestive system, is devoted to preparing the 

 food for absorption and use. This digestive system consists 

 of a food tube known as the alimentary canal and certain 

 masses of cells known as digestive glands. 



When the fish swallows food, this passes from the mouth 

 cavity into a short tube, called the gullet, and thence into a 



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Fig. 98. — Internal organs of a fish. (Carp.) 



comparatively long wide stomach (Fig. 98), which in the 

 carp extends half the length of the body cavity. From the 

 stomach extends the small intestine, which turns upon itself 



