The observation that a permanently diabetic condition may be induced in dogs by a short period of treatment with anterior pituitary extract [Young, 1937] has been generally confirmed [Campbell and Best, 1938; Houssay and Biasotti, 1938; Dohan and Lukens, 1939; Loubatières, 1939 a, b]. Subsequently it was found that changes in the islets of Langerhans of the pancreas were demonstrable in those animals in which a permanently diabetic condition had thus been established [Richardson and Young, 1938; Campbell and Best, 1938; Dohan and Lukens, 1939]. In the present paper, which is concerned with investigations on the nature of the metabolism of these diabetic dogs, the term 'pituitary-diabetes' will be used to describe the permanently diabetic condition established by such a short period of pituitary treatment, but it must be stressed that there is no intention to imply by the use of this expression that the diabetic condition is one associated