Both in the human being and in the rat an injury, such as the fracture of a long bone, causes an increased output of nitrogen and creatine in the urine. The excretion of sulphur, phosphorus and potassium is also increased, indicating a breakdown of tissue substance. This was found to be a general, rather than a local, breakdown of tissue substance [Cuthbertson, McGirr & Robertson, 1939]. In the preceding paper [Cuthbertson, Webster & Young, 1941], the ability of a crude extract of anterior pituitary tissue to induce nitrogen retention was confirmed, and it was shown that the loss of nitrogen associated with the separation in time of the carbohydrate and protein constituents of the diet of the adult rat could be more than overcome by the injection of a crude extract of the anterior pituitary glands of oxen. It was therefore of some interest to investigate the influence of such