PART FOUR 



Genetics and Human Affairs 



Genetics, like all sciences, grew originally out of man's desire to control 

 his environment. Its original exponents were stockmen, who tried to 

 improve the strains of domesticated animals, and seedsmen, who 

 needed to produce uniform seed of good quaUty. Once the theoretical 

 science has begun, it takes on a Ufe of its own, and its development is 

 not directly dependent on the solution of practical problems. The 

 application of genetics to plant and animal breeding forms a special 

 branch of the subject, requiring something more than a knowledge of 

 theoretical genetics; in particular, it is concerned with husbandry and 

 plant and animal pathology. The first chapter of this Part therefore 

 gives only a very summary account of it. The application of genetics to 

 man himself is a less speciahzed subject, and can therefore be treated 

 at somewhat greater length. 



