SIGNIFLCANCE OF STEGOMYIA FASCIATA IN WEST AFRICA. 263 



prevalent. In this connection the following quotation from Bates^ 

 'Nacuralist on the Amazons ' (p. 171, 6th ed.) may have some significance : — 



" On arriving at Para, I found that once cheerful and healthful city 

 desolated by two terrible epidemics. The yellow fever, which visited the 

 place the previous year (1850) for the first time since the discovery of 

 the country, still lingered, after having carried ofE nearly 5 per cent, of the 

 population. The number of persons who were attacked, namely, three- 

 fourths of the entire population^ showed how general is the onslaught of 

 an epidemic on its first appearance in a place. At the heels of this plague 

 came the small-pox. The yellow fever had fallen most severely on the 

 whites and mamelucos [cross-breeds, Indian and European], tlie negroes 

 •wholly escaping ; but the small-pox attacked more especially the Indians, 

 negroes and people of mixed colour, sparing the whites almost entirely, 

 and taking off" about a twentieth of the population in the course of the few 

 months of its stay.'^ 



The striking difference in the incidence of these two epidemics renders 

 it difficult to avoid the conclusion that it was due to the existence of 

 immunity, either naturally or artificially produced. If, however, the long- 

 prevalence of yellow fever in West Africa has produced a marked in- 

 susceptibility among the indigenous races, we need not anticipate the 

 occurrence of such devastating epidemics as have swept over portions of 

 Tropical America, though the disease would remain a serious menace to all 

 new-comers. 



Again, we should have to reckon with the possibility that an immune 

 negro might serve as a reservoir of the disease if introduced into a country 

 where S. fasciata occurs, but where there is no yellow fever. — Ed.] 



