108 TROPICAL MEDICINE AND HYGIENE 



after ten years' residence. A person who has not had 

 blackwater fever in an area in which the disease is 

 endemic may have his first attack after leaving that area, 

 sometimes up to six months or more after leaving it. 



Generally speaking, in Africa, it is most prevalent where 

 malaria is most prevalent, and by many persons malaria is 

 considered to be essential for the development of the 

 disease. As the disease is not known in some countries 

 where malaria is prevalent, it has either to be assumed 

 that there is a special variety of the malarial parasite 

 implicated, or that there is some special condition under 

 which this extreme haemolysis takes place. So far all 

 experiments that have resulted in a decrease in the amount 

 of malaria have been associated with a reduction in the 

 number of cases of blackwater fever. This seems to 

 hold whether the reduction is due to attacking the carriers 

 of malaria, anophelines, or to steady administration of 

 quinine. 



No morphological differences have been observed in 

 the malarial parasites in a malarious country where black- 

 water fever is endemic and in malarious countries where 

 it does not occur. The carriers differ in the different 

 countries, and in AfricaMyzoinyuifuuesta is the commonest 

 carrier in places where blackwater fever is prevalent. 



The special condition that has been considered to 

 be the immediate exciting cause is quinine poisoning. 

 The advocates of this hypothesis contend that in some 

 individuals, after they have been exposed to the endemic 

 influences, the blood is so altered that quinine produces 

 haemolysis. There are cases in which a dose of quinine, 

 even a small one, may bring on an attack of haemo- 

 globinuria ; this has been proved in many instances. 

 There are reasons for considering that this, though an 

 occasional cause of blackwater fever, is not an essential 

 or even the common cause. In many countries where 

 large doses of quinine are given, after and during fever, 

 no such effects take place. In analysing the cases 'in 

 an endemic area there is no close relation, either as 



