48 PROBLEMS OF EVOLUTION 



measles are, in most cases, immune for the rest of their lives. 

 They may come in contact with the germ, but it has no power 

 to injure them. But this immunity is not transmitted to the next 

 generation. On the contrary, we find them, as their parents 

 were, obliged each for himself to purchase immunity by suffer- 

 ing from the disease. Though, however, there is no inherited 

 immunity, there is the striking fact that in the course of genera- 

 tions the disease tends to become milder. The Fiji islanders, 

 when attacked by measles, died by hundreds. Among us the 

 deaths due to measles amount to a considerable number, but not 

 to any large proportion of the cases. Why this difference be- 

 tween English people and Fiji islanders? In the first place, we 

 must allow for the results of careful nursing. But this certainly 

 does not account for the whole difference. It is evident that a 

 race that for generations past has suffered from a disease is better 

 able to resist it than a race that is attacked for the first time. 

 This is certainly best accounted for by the fact that those who 

 were unable to combat the disease have in each generation been 

 weeded out, so that now it is coming to be looked upon rather 

 as a nuisance than a terror. Can the Lamarckians deal with these 

 facts satisfactorily ? They may contend that the increased power 

 of resistance, which is generally recognised as existing among 

 Europeans, is the acquired immunity inherited in a modified form. 

 In the case of measles and other infectious diseases which do 

 confer immunity on the sufferer, this may, perhaps, seem to hold. 

 But in the case of consumption the explanation breaks down. And 

 a principle, if it is sound, ought to be of general application. 



For hundreds of years past consumption has been one of the 

 most destructive diseases in England ; in Cromwell's time, as the 

 bills of mortality show, it was prevalent in London. In the pre- 

 sent day, probably about one in ten of the total of deaths are due 

 to some form of tuberculosis. But its destructiveness among the 

 English people is nothing to what it is among savages. If once the 

 germ is introduced among them, they have no power to resist it. 

 Now here the Lamarckian explanation is out of the question. 

 There is no acquired immunity ; a sufferer may be completely 

 cured, yet he is at least as liable to infection as a person who has 



