THE ARGUMENT FROM DISEASE 163 



275. But now, supposiDg his explanations were confirmed, 

 supposing it were proved by extended experiments that 

 parental disease does commonly affect offspring, then another 

 point would arise. What is the nature of the enfeeblement ? 

 Is it a true variation, a true alteration of hereditary tend- 

 encies ? Or is it merely an acquirement, a mere temporary 

 alteration of the germ-cell, which affects the individual which 

 arises from it, but not his descendants ? Professor Ewart 

 regards it as a variation ; but he does not appear to have 

 confirmed his hypothesis by experiments on the descendants. 

 If he is correct, then the mystery of the persistence of the 

 species in India is deepened. It becomes still more difficult 

 to understand why it was not exterminated long ago. 



276. In view, however, of this persistence of the species 

 we cannot avoid the conclusion that, however valuable Pro- 

 fessor Ewart's observations may be as elucidating questions 

 of prepotency and sterility, they do not, at any rate as yet, 

 clear up the problem of the origin of variations. 



277. It has been argued that an agency which enfeebles 

 offspring need not necessarily cause enfeeblement of the race. 

 Its effects might be counteracted by Natural Selection, which, 

 by the elimination of the unfit, might raise the specific mean 

 more than the enfeeblement of the offspring depressed it. 

 But this line of reasoning is clearly invalid. It confuses two 

 entirely distinct things, general vigour and specific resisting 

 power. To take a concrete example ; malaria causes a general 

 enfeeblement of those whom it afflicts. Presumably, if off- 

 spring are affected, they also suffer a general enfeeblement. 

 But the individuals who survive exposure to malaria are not 

 necessarily the strongest and most vigorous in a general sense. 

 They are merely those who possess the specific power of making 

 resistance to the protozoon and its toxins a power which may 

 occur in people who are otherwise weak. Thus big, strong, 

 and vigorous Englishmen do not, apparently, resist malaria 

 better than smaller and weaker men. That evolution against 

 disease is entirely specific is shown by such a fact as that 

 malaria has long afflicted races of very different physiques, and 

 that the most finely-developed Polynesian is weaker against 

 tuberculosis than the puniest Londoner. If then malaria 

 eliminated the unfit against itself and at the same time en- 

 feebled offspring, the one process would not counteract the 

 other. On the contrary, the race would lose its general 

 vigour at the same time as it increased its power of resisting 

 the disease. Evolution is never perfect. Even Africans still 

 suffer severely from malaria, almost every individual on the West 



