246 PROBLEMS OF HUMAN EVOLUTION 



by the same and other means. But the poor savage stands 

 defenceless. 



Diseases We must now again divide diseases into two classes (l) those 



microbes, ^ ue to microbes, (2) those which have a different origin. In the 



their Registrar -General's reports many of the former are called 



reduced . 



destruc- miasmatic, a term corresponding nearly or exactly to zymotic. 



tiveness But besides these, there are others which are now known to be 

 caused by germs, notably tuberculosis, pneumonia, bronchitis. 

 Sometimes in Arctic expeditions it is noticed that no one suffers 

 from catarrh, in spite of all the exposure. And it is recorded 

 that the inhabitants of an island on the coast of Scotland, in days 

 when they were visited only once annually by a ship bringing 

 supplies, found that they had each of them one cold and no more 

 per annum, and that this happened always on the occasion when 

 they had visitors which they attributed to the fact that the 

 vessel always came when the wind was in a particular quarter. 

 But the truth has now come out. 



Dividing diseases, then, on the principle just proposed we find 

 very different tendencies in the two classes. The microbic dis- 

 eases, viewed as a body, are markedly decreasing, some in 

 prevalence, others in virulence. Partly science is warding them 

 off this is a rapid process partly the race is slowly rising 

 superior to them. Such plagues as the Black Death are things 

 of the past. Small-pox and typhus claim but few, and, in each 

 decade, fewer victims. The following figures are very striking : 



Percentages of deaths due to 

 Small-pox. Typhus. 



1839 4 6-3 

 1859 '8 3-3 

 1896 -i o-i 



Scarlet fever and typhoid, though still active, show a similar 

 tendency. 



Deaths to 1, 000,000 persons living. 



1877. 1887. l8 9 6 - 



Scarlet fever 585 282 178 



Enteric fever (typhoid) 279 1 185 166 



1 A change in classification makes the exactness of this figure doubtful. But the 

 tendency is obvious. 



