The Cortical Hormone Requirement of the Adrenalectomized Dog, with Special Ref- Erence to a Method of Assay*

A method of assay for the adrenal cortical hormone utilizing the blood urea level of the adrenalectomized dog was suggested by Harrop, Pfiffner, Weinstein, and Swingle (1,2) as a result of earlier cooperative work on the effect of the hormone in the normal and adrenalectomized animal. In those studies it was found that the cortical hormone had no demonstrable effect in the normal dog. A rise in blood urea was observed to be one of the first manifestations of insufficiency in the adrenalectomized dog on the gradual withdrawal of extract. A dog unit was defined as “the minimum daily kilogram dose of cortical hormone necessary to maintain normal physiological conditions in the adrenalectomized dog for a period of 7 to 10 days; the two criteria of normal physiological condition being maintenance of body weight and blood level of non-protein nitrogen (or urea).” Rogoff and Stewart (3) had found in their studies on the effect of adrenalectomy in the dog that a significant rise in the blood urea usually terminated the “period of good health” and occurred some time (usually at least several days) before death.1 All other methods of assay so far