DURINGthe last few years the important role which the pituitary plays in carbohydrate metabolism has been demonstrated. The essen-tial physiological mechanism involves the an-terior lobe, the posterior lobe having an acces-sory and much less important action. This is contrary to what has previously been supposed. The anterior pituitary lobe is probably, after the liver and pancreas, the most important regu-lator of carbohydrate metabolism. It would, however, be a grave mistake to imagine that the only metabolic function of the anterior pituitary is its action on carbohydrates. It holds a cen-tral position in the general metabolic regulation (water, iodine, protein, carbohydrate, fat, keto-genesis, etc.), as well as having essential and important actions on the endocrine system. The alterations in the carbohydrate metabolism are especially marked in the toad, which is therefore the animal par excellence for its study. The changes appear or become accentuated about three weeksafter hypophysectomy or extirpation of the principal lobe alone. At the same time symptoms of progressive neuro-muscular asthenia develop, together with de-crease in blood sugar and glycogen which causes death in four to eight weeks, survival for months being exceptional. Implantation of the prin-cipal lobe corrects these changes and prevents death. Similar symptoms are observed in hypophysectomized rats when they become cachec-tic. In dogs the compensation apparently is better, for they can survive for months or years in an apparently good state. However, they may present mortal cachexias or hypoglycemias. Despite their good appearance their metabolism is modified, as may be demonstrated by subject-ing them to agents that induce hypoglycemia, or by producing diabetes, either by extirpation of the pancreas or by the administration of phlorhizin; these modifications affect particularly the metabolism of fasting animals. Lesions of the tuber cinereum or of the hy-