HEEEDITY IN MAN 361 



symptoms as the parents. These are cases more particularly of 

 lack of development or of premature atrophy of certain groups 

 of nerve cells.' ^ In the latter the parent may suffer from one 

 kind of disease, while the offspring may exhibit one or more of 

 a group of other diseases. This is attributed to a lack of develop- 

 ment of the highest nerve-centres as a whole. There is a lack of 

 ' perfect stability and co-ordination of various parts so that 

 according to the strains to which the individual members of 

 family are subjected, now one, now the other series of centres 

 may show itself unable to respond adequately, and one or the 

 other form of mental disturbance and nervous disease may result. 

 Here are to be included the condition of insanity, familial epilepsy 

 and the neuroses.' ^ In other words, we sometimes find stocks 

 in which there is a nervous weakness, which may manifest itself 

 in very various ways, including hysteria, epilepsy, inability to 

 control impulse, delusion, and so on. Alcoholism is sometimes 

 spoken of as though it was to be regarded as an irresistible impulse 

 to drink. Probably we should rather imagine that a condition 

 of general nervous weakness may at times manifest itself in the 

 form of a loss of control with regard to the use of alcohol. Accord- 

 ing to Mott ' there can be no doubt that neurasthenics, epileptics, 

 imbeciles, degenerates, eccentrics, and potential lunatics — all 

 those indeed with an inherent narrow margin of highest control 

 — possess a marked intolerance to the effects of alcohol '.^ Certain 

 facts are, however, very puzzling. Suicide, for example, would 

 seem to be a manner in which general nervous weakness may 

 manifest itself. Nevertheless, the tendency to suicide appears 

 sometimes as a very definite and peculiar disease which manifests 

 itself generation after generation at a certain age. Perhaps in 

 these cases we should rather see an example of how the same 

 outward circumstances — here the knowledge of the family history 

 — tends to cause a general nervous weakness to manifest itself in 

 the same way, rather than an example of a specific nervous 

 weakness.* 



4. What we know as temperament stands half-way between 

 physical and mental characters. As we have seen, temperament 

 depends upon influences exerted by the functioning of the bodily 

 organs on the nervous system and upon the peculiarities of the 



■ Adami, loc. eit., p. 26. ^ Ibid. ^ Quoted by Thomson, Heredity, 



p. 275. * Tredgold found that 80 per cent, of the mentally deticient had a 



bad nervous inheritance {Mental Deficiency, p. 40). 



