Besides giving a name to the syndrome, the cutaneous lesions of pellagra have excited the admiration and stimulated the speculations of many generations of pellagrologists. Indeed, the speculations have often taken the place of thoughtful study of the exanthem, or pellagraderm. Several factors have delayed advance in knowledge. In times past, the diagnosis of pellagra was ventured rarely except in the presence of well established lesions of the skin. Thus, the study was preponderantly of end results, since dermatitis is uncommon in mild and early deficiency. It is now known that the changes in the skin may be indolent and that they do not necessarily parallel the severity of the disease. The demonstration by Spies1 that glossitis is a much more sensitive gage than dermatitis in evaluation of therapeutic measures has properly turned the emphasis in early diagnosis from the skin. As a corollary, it has