48 MAN, THE ANIMAL 



of a mammoth mastodon or of a man should be 

 under the dominion of unicellular plants is one of 

 the most interesting of modern discoveries. 



Indeed, this is a fortunate condition. For were 

 it not so, there is a possibility that the present life 

 on earth might exhaust some of the necessary 

 chemicals such as nitrogen, oxygen, hydrogen or 

 carbon which are indispensable to the continuance 

 of life. Before these bacterial relationships were 

 solved, it was a common prediction that life would 

 have to end for the lack of suitable materials of a 

 chemical character. Now we know that this can 

 never occur, for as soon as an organism dies and 

 disintegrates the several chemicals of which the 

 body was composed return to the air and soil and 

 are ready to be used again. 



Science has been unable to discover that it makes 

 any difference how long or in what plant or animal 

 these chemicals remain. That the oxygen that we 

 breathe has been a part of the body of some other 

 organism is very probable. But after Its varied 

 relations in the protoplasm of animals, plants or 

 men, it now possesses the same chemical properties 

 and can do the same important work in living 

 protoplasm as if it had never been a part of any 

 other organism. It was not until 1893 that these 

 relationships were fully recognized. 



In a sense man's body is like a house made up 

 of different kinds of bricks. The bricks that are 



