Of the causes of hypertension in nephritis we have no exact knowledge. The theories which have been elaborated are based mainly on deductions from clinical experience or to a slight extent on experiment. Neither the clinical experience nor the experimental evidence is at all conclusive; but each in its way points to an explanation through the action of some chemical substance influencing the circulatory system. What this substance is and how it acts we do not know.
Clinically we have the very important observation that hypertension and heart hypertrophy come in that group of renal diseases in which uremia is also prone to occur, while both fail in practically all other forms, as tuberculosis, pyonephrosis, hydronephrosis, cystic kidney and the kidney of acute sepsis. In other words, hypertension, like uremia, is an evidence of renal insufficiency. It is naturally suggested that the poison of uremia is identical with that causing