Pellagra 249 



and who, in most cases, were favorably disposed towards it because 

 of the wonderful progress which had been made in the understanding 

 of other insect-borne diseases. In this country, the entomological 

 aspects of the subject have been dealt with especially by Forbes 

 (1912), and by King and Jennings, under the direction of W. D. 

 Hunter, of the Bureau of Entomology, and in co-operation with 

 the Thompson-McFadden Pellagra Commission of the Department 

 of Tropical Medicine of the New York Post-Graduate Medical 

 School. An important series of experiments with monkeys has 

 been undertaken by S. J. Hunter, of Kansas, but unfortunately we have 

 as yet no satisfactory evidence that these animals are susceptible 

 to the disease a fact which renders the whole problem difficult. 



The accumulated evidence is increasingly opposed to Sambon's 

 hypothesis of the transmission of pellagra by SimuUum. This has 

 been so clearly manifested in the work of the Thompson-McFadden 

 Commission that we quote here from the report by Jennings (1914) : 



"Our studies in 1912 convinced us that there was little evidence 

 to support the incrimination of any species of SimuUum in South 

 Carolina in the transmission of pellagra. Reviewing the group as a 

 whole, we find that its species are essentially "wild" and lack those 

 habits of intimate association with man which would be expected 

 in the vector of such a disease as pellagra. Although these flies are 

 excessively abundant in some parts of their range and are moderately 

 so in Spartanburg County, man is merely an incidental host, and no 

 disposition whatever to seek him out or to invade his domicile seems 

 to be manifested. Critically considered, it is nearer the fact that 

 usually man is attacked only when he invades their habitat." 



"As our knowledge of pellagra accumulates, it is more and more 

 evident that its origin is in some way closely associated with the 

 domicile. The possibility that an insect whose association with man 

 and his immediate environment is, at the best, casual and desultory, 

 can be active in the causation of the disease becomes increasingly 

 remote." 



"Our knowledge of the biting habits of SimuUum is not complete, 

 but it is evident, as regards American species at least, that these are 

 sometimes not constant for the same species in different localities. 

 Certain species will bite man freely when opportunity offers, while 

 others have never been known to attack him. To assume that the 

 proximity of a SimuUum-breedmg stream necessarily implies that 

 persons in its vicinity must be attacked and bitten is highly fal- 



