Pellagra 
251 
“In May, 1913, in company with Capt. J. F. Siler of the Thomp- 
son-McFadden Pellagra Commission, I visited the region of which 
Midland in Midland County is the center. This region is very dry 
and totally devoid of running water for a long distance in every 
direction. The only natural source of water-supply, a few water 
holes and ponds, were visited and found to be of such a nature that 
the survival of Simulium, far less its propagation in them, is abso¬ 
lutely impossible. The nearest stream affording possibilities as a 
source of Simulium is 60 miles away, while the average distance of 
such possibility is not less than 100 miles.” 
“Artificial sources of water-supply were also investigated care¬ 
fully and were found to offer no opportunity for the breeding of 
Simulium." 
“At Midland the histories of five cases of pellagra were obtained, 
which gave clear evidence that this place or its immediate vicinity 
was the point of origin. Persons of long residence in the country 
were questioned as to the occurrence of such flies as Simulium and 
returned negative answers. These included a retired cattle owner, 
who is a man of education and a keen observer, an expert veterinarian 
stationed in the country who has the cattle of the country under 
constant observation, and a practical cattle man, manager of a ranch 
and of wide experience. The latter had had experience with ‘Buf¬ 
falo gnats’ in other localities (in the East) and is well acquainted 
with them. His close personal supervision of the cattle under his 
charge, makes it practically certain that he would have discovered 
these gnats had they been present in the country.” 
“At the time the study was made, Simulium was breeding and 
active in the adult state in the vicinity of Dallas, Texas, in the 
eastern part of the state. We have here a region in which cases of 
pellagra have originated, yet in which Simulium does not and cannot 
breed.” 
Other possible insect vectors of pellagra have been studied in 
great detail and the available evidence indicates that if any insect 
plays a role in the spread of the disease, Stomoxys calcitrans most 
nearly fills the conditions. This conclusion was announced by 
Jennings and King in 1912, and has been supported by their subse¬ 
quent work. 
Yet, after all the studies of the past decade, the old belief that 
pellagra is essentially of dietary origin is gaining ground. Gold- 
berger, Waring and Willets (1914) of the United States Public Health 
