220 TRANSMISSION OF ACQUIRED CHARACTERS 



on the parent's body are in the strict sense transmitted to the 

 offspring, we do well to consider — (i) that the intemperate habits 

 of the parent may be the expression of an inherited psychopathic 

 disposition, and it is this which is transmitted to the offspring ; 

 (2) that the saturation of the body with alcohol may have a 

 direct effect on the nutrition and developmental vigour of the 

 germ-cells ; (3) that the children of drunkards often become 

 accustomed to alcohol as part of their food, from the days of 

 suckling onwards. 



Nervous Diseases. — Prof. Binswanger of Jena, a famous 

 student of psychiatry, has expressed his inability to find evidence 

 that a mental or nervous disease acquired during the individual 

 life is, as such, or in partial expression, inherited by the offspring. 

 There are, he of course allows, numerous cases in which an 

 inheritance of mental or nervous diseases can be traced from 

 one generation to another ; but his difficulty was to find a case 

 where it could be securely maintained that the first occurrence 

 of the disease was due to external influence. 



It may, of course, be urged, though it seems an untenable 

 extreme, that mental and nervous diseases never have an exo- 

 genous origin, but are always referable to germinal defect. If 

 so, it simply forces us to say that this line of argument is closed 

 as far as the question of the transmissibility of modifications is 

 concerned. 



Modifications of Habits and Instincts. — Many animals are 

 very plastic in their habits, and some show some plasticity even in 

 their instincts. It seems an interesting line of experiment to 

 try to determine whether there is any evidence of transmission 

 of peculiar individually modified habits. For an expert discus- 

 sion of the subject we must refer to Principal Lloyd Morgan's 

 Habit and Instinct. 



There are obviously many difficulties. The experimenter 

 must be sure that the original change of habit is really modifica- 

 iional, not an inborn idiosyncrasy. He must be careful to 



