CHEMICAL CONDITIONS 



59 



TABLE II 

 SHOWING THE DISTRIBUTION AND SOLUBILITY OF ATMOSPHERIC GASES 



Nitrogen has little effect upon animals except when present in excess. 

 Under these conditions in the laboratory, bubbles of the gas accumulate 

 in the tissues and blood-vessels of fishes and cause death. It is not 

 certain that such conditions exist in nature (Fig. 9). 



Oxygen is usually necessary to the life of animals. Most animals 

 that have been studied select water with a rather high oxygen content 

 instead of water with little or no oxygen. The resistance of animals to 

 lack of oxygen varies in different groups. It has been found that water 

 with about 6 c.c. of oxygen and 14 c.c. of nitrogen per liter is suitable 

 for brook trout. Mackinaw trout have been taken in water containing 

 but i c.c. of oxygen per liter (6). 



In general, carbon dioxide is a narcotic in its action upon animals. 

 In small quantities it is a stimulant, especially to respiratory action. 

 In large quantities it produces anesthesia and death. Several workers 

 have shown that carbon dioxide is very toxic to fishes. Most aquatic 

 animals that have been studied turn back when they encounter water 

 containing large amounts of the gas. This turning away from carbon 

 dioxide is much more decided than it is in the case of corresponding 

 differences (24 c.c. per liter) in oxygen content. Fishes, for example, 



