1. Isolated cases of a
dermatitis resembling histologically that of human
pellagra have occurred in rats supplied with sufficient
vitamin B(2) (G) in the form of beef extract or neutral autoclaved yeast to produce good growth. 2. Other rats on basal diets containing similarly prepared nutrients but deprived of any known source of
vitamin B(2) (G) develop a
dermatitis similar in appearance to that described by other workers, but this skin effect differs in histological picture from that found in human
pellagra or in
black tongue of dogs. These rats showed growth failure which supports the view that they lacked growth-promoting
vitamin B(2) (G). 3. It is suggested that
dermatitis in rats may be of diverse type; one resulting from
vitamin B(2) (G) deficiency quite different histologically from human
pellagra, and one closely allied to human
pellagra and
black tongue in dogs due to lack of some at present unidentified factor.