230 GENETICS 



these except two have been of normal mentality and 

 these two were not feeble-minded. . . . The fact 

 that the descendants of both the normal and the 

 feeble-minded mother have been traced and studied 

 in every conceivable environment, and that the re- 

 spective strains have always been true to type, tends 

 to confirm the belief that heredity has been the 

 determining factor in the formation of their respec- 

 tive characters." 



4. MORAL AND MENTAL CHARACTERS BEHAVE 

 LIKE PHYSICAL ONES 



These instances of human breeding show unmis- 

 takably that "blood counts" in human inheritance, 

 even though the hereditary unit characters that lead 

 to these general results have not yet been analyzed 

 with the clearness that is possible in dealing with the 

 characters of some animals and plants. 



There is of course no question of moral and mental 

 traits in plants, and the role that these play in animals 

 is not easy to determine ; but in man the case is 

 undoubtedly much more important and complex, 

 since mental and moral characteristics have a large 

 share in making man what he is. There is, however, 

 no fundamental scientific distinction which can be 

 drawn between moral, mental, and physical traits, 

 and they are undoubtedly all equally subject to the 

 laws of heredity. 



For instance, as an illustration of the heritability 



