Glucose evoked significant hyperglycemia in the frog, Rana tigrina, 0.5 h after the injection and it took a longer time to regain normoglycemia than mammals, thus exhibiting a low glucose tolerance. The islet tissue of injected animals showed degranulation and atrophy of /?-cells only, the α-cells remained almost normal. This damage suggests that the β-cells of this frog are functionally like those of mammals and other vertebrates, and secrete insulin. A single dose of glucose was found incapable of producing permanent diabetes, and β-cells damage was repairable at later stages. Excess of glucose in the blood seems to stimulate secretion of insulin by the β-ce