INTRODUCTION
The extensive records accumulated during the field study of pellagra in Spartanburg County, S. C., have presented an opportunity to inquire into the behavior of this disease in a population of considerable size living under natural conditions of civil life. Such an inquiry might be expected to contribute something to the general prognosis of pellagra in the population of the county and in the Southern states as a whole and it might even bring to light some facts of value in the prognosis in an individual case of the disease. Manifestly, also, it is desirable to know fairly well the course of the disease as a biological phenomenon, uninfluenced by intentional drugging, dieting or climatic changes, in order to estimate the possible influence which these latter may exert on the course of pellagra. Fortunately for the purpose of such a study, a considerable proportion of