METHODS 41 



First we establish a simple law for the fall of a body in 

 vacuo ; but such a law can be only approximate the 

 moment there is question of falling in air. Then we try to 

 find another formula to express retardation from the friction 

 of the air ; and by this we correct our first formula. 



In each case, for a real and single phenomenon which is 

 complicated only in our analysis, we have substituted an 

 artificial superposition of two imaginary phenomena, each 

 of which it is easy for us to represent by formulae. This is 

 the same fanciful method of analysis of which I spoke before ; 

 it is useful only in the human study of a fact. 



Mariotte's Law gives us an example of another Approxi- 

 mate Law ; and in this case men of science have not yet 

 been able to find a complementary formula to correct, for 

 each gas, the inexactness of the law. 



In spite of its imperfections, we shall make use of this 

 method in studying life because it pleases the human 

 mind. We shall even begin by it and devote the next part 

 of our work to the application of this artificial method of 

 Approximate Laws in seeking for the essential biological 

 phenomenon. It will not upset readers who are accustomed 

 to the method in their studies of physics and chemistry ; 

 and by means of it we shall discover the approximate law 

 of assimilation or heredity. 



In the next part we shall enter into the heart of our sub- 

 ject by applying the more rational method of studying the 

 relation of living bodies with other colloids ; and then we 

 shall establish a law, this time rigorously scientific, which we 

 may call functional assimilation, habit, or heredity of acquired 

 characters. 



