Insulin hyperglycemia offers a means of determining the sensitivity of the rabbit to insulin, without subjecting it to insulin convulsions. As a rabbit changes in its sensitivity to insulin, its initial response to insulin changes accordingly, The c/o drop in blood sugar, 4 hr. after the injection of 2 units of insulin per kgm. of body-weight, is related to the time of onset of convulsions. The time of onset of convulsions, following insulin injection, is in no way related to the initial blood sugar concn. The greater the sensitivity of a rabbit to insulin, as measured by the time of onset of convulsions, the greater the amt. of glucose which must be injected to prevent subsequent convulsions. The [female] rabbit is more sensitive to insulin than the [male] both in its initial response to insulin injection and in its subsequent responses to repeated insulin injections. The [female] is more constant in its responses to insulin injection than the [male].