Extirpation of the pancreas in man has been shown by William T. Bull to sometimes produce diabetes, and experimental extirpation of this gland in dogs has the same result. In many, but not all fatal cases of diabetes, more or less pancreatic disease, usually of the nature of chronic interstitial inflammation, has been observed. The gland is known to produce an internal secretion - i. e., a secretion passed into the circulation, which is a glycolytic ferment - and when the gland is diseased this ferment is reduced in quantity, sugar fails of conversion to glycogen, and diabetes results. Opie believes that the islands of Langerhans are the structural portions of the pancraes concerned with the production of the ferment, and degenerative changes have been observed in diabetes in these islands of polygonal cells which are supplied with a rich capillary network.