170 The Mechanistic Conception of Life 



mainly a metaphorical value, but they serve to emphasize the 

 two facts, that the three salts, NaCl, KCl, and CaCl^, exist in 

 our blood in the same relative proportion as in the ocean and that 

 they seem to play an important role in the maintenance of life. 

 I intend to put before you a series of experiments which 

 seem to throw some light on the mechanism by which the 

 solutions surrounding living cells influence their duration of life. 



II 



In order to give a picture of the extent to which the life of 

 many animals depends upon the cooperation of the three salts I 

 may mention experiments made on a small marine crustacean, 

 Gammarus, of the Bay of San Francisco. If these animals are 

 suddenly thrown into distilled water, their respiration stops 

 (at a temperature of 20° C.) in about half an hour. If they are 

 put back immediately after the cessation of respiration into 

 sea-water, they can recuperate. If ten minutes or more are 

 allowed to elapse before bringing them back into the sea-water, 

 no recuperation is possible. Since in this case death is caused 

 obviously through the entrance of distilled water into the 

 tissues of the animals, one would expect that the deadly effect 

 of distilled water would be inhibited if enough cane sugar were 

 added to the distilled water to make the osmotic pressure of 

 the solution equal to that of the sea-water. If, however, the 

 animals are put into cane-sugar solution, the osmotic pressure 

 of which is equal to that of sea-water, the animals die just 

 about as rapidly as in distilled water. The same is true if the 

 osmotic pressure of the sugar solution is higher or lower than 

 that of the sea-water. The sugar solution is, therefore, about 

 as toxic for these animals as the distilled water, although in the 

 latter case water enters into the tissues of the animal, while 

 in the former case it does not. 



If the sea-water is diluted with an equal quantity of distilled 

 water in one case, and of isotonic cane-sugar solution in the 



