-10- 



which has given any return for work spent on it is the sand fly and I 



am of the opinion that the relation of this insect to disease would 



repay further investigation" (1915, p. 949). 



Perhaps stimulated by Mackie's suggestion and following the 



example of Sergent _et a_l_. (1921) in their work on oriental sore 



in Algeria, Sinton (1922) studied the distribution of Indian sand 



flies and found that the distribution of kala-azar showed striking 



congruence with that of _P. argentipes Annandale and Brunetti; he 



considered this sand fly to be the most likely vector. In 1924, a 



"Kala-azar Commission" was set up under the directorship of 



Christophers, and its members were soon successful in rearing this 



most likely suspect in the laboratory. Once a laboratory colony was 



established, Knowles et al. (1924) fed specimens of these sand flies 



on patients with kala-azar and found that a heavy flagellate infection 



developed in P. argentipes ; they noted that the same degree of 



infection did not occur in other Phlebotomus species. The following 



year Shortt et a_l_. (1926), working with L donovani , demonstrated that 



in _P. argentipes the infection passes forward in the fly to the buccal 



cavity and proboscis. For the next five years, Shortt and co-workers 



of the Kala-azar Commission conducted three series of transmission 



experiments using human volunteers and Chinese hamsters as hosts. 



They fed an astounding 79,939 artificially infected £. argentipes on 



either human volunteers or hamsters but reported negative results as 



follows: 



The failure of any of the subjects of experiment to show 

 infection with kala-azar ... is very difficult to explain if 

 the theory of Phlebotomus transmission is to be maintained. We 

 can only suppose that some essential factor in the process of 

 infection has been omitted in our experiments which is present 

 under natural conditions, or that the vast amount of labour 

 expended by us . . . during a period of 5 years has been expended 



