278 HEREDITY AND DISEASE 



logical evidence that alcoholic poisoning may prejudicially affect 

 the germ-cells, but it is more difficult than most people think 

 to substantiate this from human cases. Thus in the case of 

 intemperate mothers we have to allow for the deranged nutrition 

 as well as for the poisoning, and for the poisoning of the embryo 

 through the placenta as well as for a possible direct deterioration 

 of the germ. 



(12) There is some evidence that deterioration in the offspring, 

 as marked by epilepsy, some forms of insanity, lack of control, 

 feeble-mindedness, deaf-mutism and stunted growth, is apt 

 to be intensified and to appear earlier if the parents are alcoholic. 



Nervous Diseases. That the nervous system is particularly 

 liable to disease is well known, and various reasons have been 

 assigned for this, (i) Nervous organs are of all organs the 

 most intricate in their complexity, and nerve-cells are the most 

 highly differentiated cells. But a high degree of complexity 

 involves greater instability, greater liability to accident. A 

 free-wheel bicycle with two or three grades of gearing is a finer 

 mechanism than, let us say, the old-fashioned high bicycle, 

 where even the complexity of a chain was avoided ; but there 

 is in the increased excellence the inevitable disadvantage of 

 a greater range of possibility "for something going wrong." 

 (2) Nervous organs* have a very limited power of regeneration 

 after injury. There is no increase in the number of our nerve- 

 cells after we are born, and reports of cases of regeneration of 

 nerve-cells after injury are few and far between as regards 

 backboned animals. (3) Characters of recent origin tend to 

 be more unstable than those of ancient date, and the differentia- 

 tion of man's brain is relatively recent compared with that 

 of his food-canal. Prof. Adami (190-1, p. 1319) refers to the 

 discovery made by James Ross of Manchester that " when there 

 is progressive atrophy of the cells in the cortex of the brain, 

 the first motor-cells to show signs of that atrophy are those 

 governing the muscles which differentiate man from other 



