"In May, 1913, in company with Capt. J. F. Siler of the Thompson-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 absolutely 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 carefully 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 'Buffalo 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 rôle 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 subsequent work. Yet, after all the studies of the past decade, the old belief that pellagra is essentially of dietary origin is gaining ground. Goldberger, Waring and Willets (1914) of the United States Public Health Service summarize their conclusions in the statement, (1) that it is dependent on some yet undetermined fault in a diet in which the animal or leguminous protein component is disproportionately large and (2) that no pellagra develops in those who _consume_ a mixed, well-balanced, and varied diet, such, for example, as that furnished by the Government to the enlisted men of the Army, Navy, and Marine Corps. Leprosy