HUMAN DISEASES 523 



authorities maintain that the disease results from persistent serious 

 attacks of malaria, some from excessive dosage with quinine, and 

 others that it is due to a bacterium, while at one time it was 

 thought that a specific protozoal infection might be involved. 

 Blackwater is now regarded as a concomitant of malaria, though 

 persons who were known never to have had malaria or taken 

 quinine have suffered from it. Professor J. Gordon Thomson 

 (1923 and 1924) studied the disease in Southern Rhodesia and 

 summarized the knowledge then existing, and this work was con- 

 tinued during 1925 to 1929 by G. R. Ross (1932). A marked 

 advance in the treatment of the disease was made by the introduc- 

 tion of blood transfusion, and further work on these lines has been 

 done in Southern Rhodesia during the last few years. In particular 

 the reticulocyte response to this method of treatment has been 

 worked out at the public health laboratory at Salisbury. A 

 society of blood-donors has been formed for this purpose. Black- 

 water fever is found chiefly amongst prospectors or others whose 

 occupation exposes them to mass infection by malaria-carrying 

 mosquitoes in circumstances where the living conditions are un- 

 satisfactory. The number of fatal cases in Southern Rhodesia from 

 1930 to 1935 ranged from twelve to seventeen annually. In the 

 Belgian Congo it has been proved that the majority of cases 

 occur among Europeans who live in malarial districts, but who 

 do not take quinine as a prophylactic. Professor J. W. W. 

 Stephens, aided by a grant from the Leverhulme trustees, is to 

 prepare a treatise on the disease in its historical and other 

 aspects. 



YELLOW FEVER 



Yellow fever, also a mosquito-borne disease, is to some extent 

 capable of similar methods of investigation and control. Its 

 history and epidemiology are described at length by H. R. Carter 

 (1931) and the many problems raised by the disease in Africa are 

 discussed by Ricardo Jorge (1934). It has been conclusively 

 proved, in South America, that Aedes is not the only vector, since 

 outbreaks have occurred in localities where it is absent. In such 

 cases the vector appears to be some other mosquito, perhaps Ano- 

 pheles. Yellow fever is therefore now divided into two classes: 



