4 MAN, THE ANIMAL 



take into consideration: i, that living protoplasm 

 is so complex that it has not been accurately anal- 

 yzed to date; 2, that there is no other form of 

 matter which is as complex as living protoplasm; 

 and 3, that no exact method has been devised for 

 studying that which we know as the life of proto- 

 plasm. These facts compel biologists to write in a 

 more general manner than the chemist, but even 

 he, the chemist, finds it impossible to be specific all 

 of the time. Notwithstanding the complexity and 

 difficulty of the problem, we can say that there is 

 a science of biology which biologists, themselves, 

 regard as well established, with its own methods 

 and technical language. During the growth of 

 the science of biology for the past hundred years, 

 and we should keep in mind that biology is one 

 of the younger sciences, a number of generaliza- 

 tions or fundamental laws have come to be ac- 

 cepted by all students of life. These we shall 

 try to state and to indicate their bearing upon 

 man. 



The mere fact that certain given events can be 

 formulated into a law places definite restrictions 

 around their relation to one another. We say, for 

 example, that Halley's comet will complete its 

 orbit in 75 years, which fact expresses a law about 

 the way this comet moves. In a similar way we 

 are able to state certain laws about the life com- 

 mon to all living things ; and as we do this, definite 



