THE MOST recent theories concerning the causative factors in experimental renal hypertension and their interrelationships may be stated as follows:
1. Renin, a protein-like substance, is formed in excessive amounts by an "ischemic" or "anoxemic" renal parenchyma. Hypertensinogen, the precursor of hypertensin, is a substance of the alpha-globulin fraction of the plasma which has been demonstrated to be formed in the liver and has a specificity for reacting with renin, produced in the kidney, to form hypertensin, the vasopressor substance.
2. The existence of a hitherto undescribed homeostatic system for the regulation of the peripheral circulation has been disclosed in studies by Shorr, Zweifach and Furchgott.1 "This system is made up of two components, one of hepatic (V. D. M.), the other of renal origin (V. E. M.). Evidence of the presence of such a circulatory homeostatic system, its mode and sites of origin, and the manner in which