SCOPE OF GENETICS 33 



invasion of a pathogenic organism, wheat- 

 rust, is due to the presence of one of the 

 simple factors or ingredients of which I have 

 spoken, and what we know to be true in that 

 one case we are beginning to suspect to be 

 true of resistance to certain other diseases. 

 No pathologist can see such an experiment 

 as this of Professor Biffen's without realizing 

 that here is a contribution of the first im- 

 portance to the physiology of disease. 



There is no lack of utility and direct 

 application in the study of Genetics. I have 

 alluded to some strictly practical results. If 

 we want to raise mangels that will not run to 

 seed, or to breed a cow that will give more 

 milk in less time, or milk with more butter 

 and less water, we can turn to Genetics with 

 every hope that something can be done in 

 these laudable directions. But here I would 

 plead what I cannot but regard as a higher 



B. 3 



