Introduction 5 



trade as their fathers, the reappearance of the disease is not 

 necessarily a case of heredity at all. It is the external con- 

 ditions which are hereditary rather than the disease. 



But even if we allow that a disease whether physical or 

 moral is a matter of heredity, or rather the predisposition 

 to that disease because a disease as such is never inherited 

 then what is our position ? 



"i. If it does not find appropriate nurture, it will not 

 express itself. 



2. Or it may lie latent and express itself in the next 

 generation. 



3. Or it may eventually disappear altogether.'* 



In Professor James' famous chapter on " Instinct " l there 

 is an illustration of the " inhibition " of certain instincts through 

 want of appropriate " stimuli." He relates the case of a young 

 puppy removed from a stable, where he had been wont to 

 burrow in the earth for a hidden bone, to a lady's drawing- 

 room. For a day or two the puppy amuses himself at the 

 same game, but the appropriate stimuli are all missing. A 

 glove is a poor substitute for a bone ; the carpet is not the 

 stable floor, and, as the puppy has been regularly fed, the 

 chief incentive of hunger is also missing. Eventually he 

 loses interest in his purposeless game, and the instinct is 

 inhibited ; so that when similar stimuli reappear in later life 

 he will not respond. The analogy is obvious. 



Let us suppose the child of' a thief inherits his father's 

 criminal instincts which is doubtful or suppose that he has 

 himself been convicted of petty theft. If removed from his 

 unsatisfactory surroundings to a decent home, given a dif- 

 ferent standard of behaviour, and trained in habits of obe- 

 dience and self-control, when the temptation comes to him 

 in later life the instinct will probably be inhibited. It will 

 be inhibited because the appropriate " stimuli " supplied by 

 his early environment, which, put briefly, were the forces of 



1 Principles of Psychology, vol. ii. p. 339. 



