78 INFECTIOUS AND PARASITIC DISEASES. 



highly disastrous, as witness the terrible ravages of 

 measles among the natives of the Faroe Islands in 1846, 

 when out of 7,782 people, 6,000 were attacked; and also 

 the invasion of the Fiji Islands in 1875 by the same 

 malady, during which 40,000 of its 150,000 inhabitants 

 died. Nor is it necessary to cite examples of distant 

 peoples; in our own country we have an object lesson 

 in the Negro and the Indian. The Negro is three times 

 as susceptible to tuberculosis as the white inhabitants; 

 and the North American Indian has been well-nigh 

 exterminated by this ''great white plague." Generally 

 speaking, the longer the contact of a race with an 

 infectious disease, the less is its predisposition to it. 

 Tuberculosis well illustrates this point in the respect 

 that the most ancient race, the Jews, suffers least from 

 it; other races, in inverse ratio to their antiquity. 

 Diminution in susceptibility through contact is prob- 

 ably brought about by large numbers of individuals in 

 successive generations surviving an infection, and 

 transmitting to succeeding generations their own individ- 

 ual resistance, together with that acquired by passing 

 through an attack of the disease. Yet after every 

 factor, such as surroundings, food, contact with a 

 disease, etc., has been considered, there is still wanting 

 an explanation of the fact that when two races live 

 side by side, under precisely similar circumstances, 

 the one suffers from an infectious disease to a greater 

 extent than does the other. Upon no other grounds than 



