The Life of the Fish 1 1 



channel through which the great spinal cord passes, and above 

 and below are a certain number of processes or projecting 

 points. To some of these, through the medium of another set of 

 sharp bones, the fins of the back are attached. Along the sides 

 of the body are the slender ribs. 



The Fish in Action. The fish is, like any other animal, a 

 machine to convert food into power. It devours other animals 

 or plants, assimilates their substance, takes it over into itself, 

 and through its movements uses up this substance again. The 

 food of the sunfish is made up of worms, insects, and little fishes. 

 To seize these it uses its mouth and teeth. To digest them it 

 needs its alimentary canal, made of the stomach with its glands 

 and intestines. If we cut the fish open, we shall find the stomach 

 with its pyloric caeca, near it the large liver with its gall- 

 bladder, and on the other side the smaller spleen. After the 

 food is dissolved in the stomach and intestines the nutritious 

 part is taken up by the walls of the alimentary canal, whence 

 it passes into the blood. 



The blood is made pure in the gills, as we have already seen. 

 To send it to the gills the fish has need of a little pumping-engine, 

 and this we shall find at work in the fish as in all higher animals. 

 This engine of stout muscle surrounding a cavity is called the 

 heart. In most fishes it is close behind the gills. It contains 

 one auricle and one ventricle only, not two of each as in man. 

 The auricle receives the impure blood from all parts of the body. 

 It passes it on to the ventricle, which, being thick-walled, is 

 dark red in color. This passes the blood by convulsive action, 

 or heart-beating, on to the gills. From these the blood is col- 

 lected in arteries, and without again returning to the heart it 

 flows all through the body. The blood in the fish flows slug- 

 gishly. The combustion of waste material goes on slowly, and 

 so the blood is not made hot as it is in the higher beasts and 

 birds. Fishes have relatively little blood; what there is is 

 rather pale and cold and has no swift current. 



If we look about in the inside of a fish, we shall find close 

 along the lower side of the back-bone, covering the great artery, 

 the dark red kidneys. These strain out from the blood a cer- 

 tain class of impurities, poisons made from nerve or muscle 

 waste which cannot be burned away by the oxygen of respiration. 



