Abstract
Daily subcut. injns. of cortisone or of ACTH increased the wts. of the islets of Langerhans in hypophysectomized rats. In intact rats the absolute effect, though present, was not great, but when ACTH was given by continuous intraven. infusion the islet increase was very much greater. The adrenals also were more strongly affected. It is concluded that both cortisone and ACTH stimulate islet growth and that the method of admn. of these materials is very important in determining their influence.