XI] 



CAUSAL AGENT 



193 



the form of small hyaline bodies, occurring in the red cells, 

 which he considered to be related to Babesia. In addition, he 

 fed Culex fatigans on infected patients and claimed to have 

 found his parasites in the insects up to the fifth day after 

 feeding, without, however, observing any signs of their develop- 

 ment. Nevertheless the salivary glands were said to contain 

 spores from two days up to a month after the mosquito had 



Fig. 52. The distribution of Culex fatigans. 



fed on infected blood. A typical attack of dengue was pro- 

 duced in a healthy person by the injection of the salivary 

 glands of a mosquito, that had fed on an infected patient 

 24 hours previously. 



Although Graham's work on the transmission of dengue by 

 Culex fatigans has been confirmed, the organism which he 

 described has never been observed by any subsequent investi- 

 gators, but from the nature of the disease there seems little 

 doubt that it is caused by some protozoal parasite living in 

 the blood. Ashburn and Craig have studied the aetiology 



H. B. F. 13 



