Although the response of the adrenal gland to excessive intakes of protein has been studied on many occasions (Fahr, 1912; Tepperman, Engel & Long, 1943;Ingle, Ginther & Nezamis, 1943;Ingle, 1945;Benua & Howard, 1945; Leathem, 1945 Leathem, , 1947 Korpbsy, 1952), there are few publications dealing with the effects of protein deficiency on the gland. I n an early series of studies, Limson & Jackson (1932) fed young rats for several months on a diet low in protein which inhibited growth; adrenal weight was reduced by 77,, which was regarded as insignificant. Leathem (1958) found that the adrenal glands of immature rats fed for 30 days on a proteinfree diet were much smaller than the glands of rats fed for a similar period on a diet containing 20 of protein; however, this difference was inverted when the weights of the glands were expressed in relation to the final weights of the rats. In some unpublished experiments, Orton (1937) is reported by Tepperman et al. (1943) to have found no difference in the ratio of adrenal weight to body-weight between growing rats fed ad lib. on a diet containing 3.5% protein and those on a diet containing I 8% protein. When calorie intake on the two diets was restricted to that consumed by the rats on the 3'5% protein diet, those on the 18% protein diet had larger adrenal glands. This experiment suggests that calorie intake may be a significant factor which modifies the response of the adrenal gland to dietary protein intake.These experiments do not provide information about the influence of dietary protein level on individual chemical constituents of the adrenal gland, which may be affected independently of gross changes in gland weight. We have accordingly carried out experiments to determine the effect of complete removal of protein from the diet on the size of the adrenal gland and its content of protein, phospholipid and nucleic acids. Secondly, the possibility that calorie intake modifies the effect of dietary protein content on adrenal function has been examined. Thirdly, we have determined whether the response of the gland to the stimulus of adrenocorticotrophic hormone (ACTH) is affected by the protein and calorie content of the diet. The experiments carried out by previous investigators were confined to growing rats, usually fed on the diets over long periods, and in consequence the interpretation of the action of diet on adrenal weight in these experiments is complicated by large differences in body-weight between groups on different diets. Our experiments were; therefore, carried out on more https://www.cambridge.org/core/terms. https://doi