THE BIOLOGICAL UNIT 49 



used to build a house can also be used to build a 

 factory, a saloon, or a church. In each relation, 

 they serve their part, but the bricks do not consti- 

 tute the building. The building may be used suc- 

 cessively as a church, a clubhouse or a saloon, as 

 the purpose of the owner at the time may dictate. 

 It is the peculiar life of the plant like a rose, the 

 life in a horse or in man that makes the difference, 

 and not in the material out of which each is con- 

 structed. 



The life of this biological plant unit is as the 

 simple ameba, like the life in the cells in man's 

 body. Even this brief review of their services to 

 other forms of life reveals one of those close re- 

 lationships that is more important than the differ- 

 ences that exist between man and other forms of 

 life. Man's dependence on the work of bacteria 

 alone justifies the earlier statement that man has 

 more in common with such forms of life than he 

 has, that differs. In this study of the biological 

 unit, one of the fundamental categories of life, a 

 deeper understanding of man's organization is 

 gained. It clearly indicates that man does not exist 

 apart from and distinct from other forms of life. 



Science has no answer to the question, why life 

 should be confined within the limits of cells or 

 why all vital phenomena should be carried on 

 in such microscopic compartments. But science 

 has been able to discover that every living thing 



