1. An improved method of preparing anti-insulin guinea pig serum of high potency is described.
2. Glucose metabolism has been studied in the perfused hearts of rats pretreated with anti-insulin serum. In perfused hearts taken from rats one hour after the injection of 0.5 ml. of anti-insulin serum there was a significant decrease in total glucose uptake, in glucose oxidation and in the lactate and glycogen formation from glucose as compared with values obtained in perfused hearts from normal rats.
3. When insulin was added to the perfusion fluid no significant differences were observed in glucose metabolism in perfused hearts from anti-insulin treated rats and from normal rats.