1 84 THE TREND OF THE RACE 



whooping cough, measles, scarlet fever and diphtheria are very 

 prevalent among all classes. The mortality of the first three is 

 much greater among the children of the poor, whereas diphtheria 

 when allowed to run its natural course has a high mortality among 

 rich and poor alike. With measles and whooping cough mortality 

 is largely dependent upon general health, whereas with diphtheria 

 this is not nearly so obvious. 



Some epidemic diseases are doubtless selective in their nature, 

 ehminating to a greater degree those with weakened constitutions, 

 whereas others apparently possess little selective value so far as 

 can be observed. Some diseases, therefore, may be racial bles- 

 sings in disguise, whereas others may have simply a depressing 

 influence on the race as a whole. There is evidence to show that 

 in the white race there are different degrees of susceptibility to 

 several diseases correlated with differences in the degree of pig- 

 mentation. Baxter, in his study of large numbers of soldiers of 

 the Civil War, concluded that those with a light complexion were 

 more liable to disease and suffered more from their injuries than 

 those with a dark complexion. The proportions of recruits re- 

 jected for military service were, among the blonds, 385.2 per 

 thousand, and among the dark complexioned, 325 per thousand. 

 Eye troubles in the two classes were in the proportion of blonds 

 22 and dark 18. In Scotland, according to Tocher, the incidence 

 of insanity is greater among the people of light colored eyes. 

 McDonald has studied the relation between pigmentation and 

 disease in a large number of children in the hospitals at Glasgow. 

 He finds that in regard to diphtheria, whooping cough, scarlet 

 fever and measles, *'the dark-haired, dark-eyed child has consid- 

 erably more recuperative power than the fair-haired, light-eyed 

 child. The medium-haired medium-eyed child occupies an inter- 

 mediate position as regards recuperative power." "The closer 

 the type approximates the fair, the less recuperative power it has, 

 and the less resistance it offers to the diseases." 



These results are quite parallel to what has often been observed 

 among animals. Darwin states on the authority of Professor 

 Wyman that dark pigmented swine in Virginia eat with impunity 



