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 Simulium. 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 Simulium 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 Simulium 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 Simulium -breeding stream necessarily implies that 
persons in its vicinity must be attacked and bitten is highly fal- 
