278 HEREDITY AND DISEASE 



to the conclusion that the germ-cells may (in cases of extreme 

 alcoholism) be prejudicially affected along with the body of 

 the victim. As it is often only the father who is alcoholic, it 

 follows that the poisoning influence, whether of the alcohol 

 itself or of by-products resulting from the nutritive disturb- 

 ances which its abuse provokes, may affect the germ-cells as 

 such. What exactly the effect is we do not know, but in some 

 measure the germ-cells are probably weakened, or poisoned, or 

 deranged. " This direct deterioration of the germ is a patho- 

 genic factor of the first rank " (Martius, 1905, p. 23). For if 

 the germ-cells are affected the offspring will also be affected. 



NerYOUs 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 (1901, 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 



