HISTORY 



1231 



they could obtain, and therefore came to the conclusion that the 

 causal agent of the disease must be of ultramicroscopic size. 



In 1909 Seidelin described the presence of minute bodies [Paraplasma 

 ■ftavigenum) in the red cells of persons suffering from yellow fever, but these are 

 not believed to have anything to do with yellow fever. Low and Wenyon 

 have shown that SeideUn's bodies are common in the blood of young 

 guinea-pigs. 



Fig. 628. — Map of the Distribution of Yellow Fever. (After Newstead.) 



A. 



Fig. 629. — -The Distribution of Stegomyia calopus. (After Newstead.) 



The theory of the propagation of the disease by Stegomyia 

 calopus has been put to the practical test of prophylaxis with most 

 excellent result's in Havana, Texas, Mexico, and New Orleans, and 

 in the works of the Panama Canal. The late Sir Rubert Boyce 

 did excellent work in drawing attention to the yellow fever of 

 West Africa, where it is extremely deadly at times, and which is 

 probably a secondary endemic centre. 



