Determination of blood pressure has become a procedure of importance in the practice of medicine. One may not agree entirely with Cabot's1 dictum that "though one of the simplest, it is the most important of all medical tests." The variability in the findings of physicians attests the crudeness of many of the current measurements of blood pressure in man, so that it almost appears at times as if simplicity and speed had been substituted for calculated accuracy. Furthermore, it seems rash to overlook the readings of the clinical thermometer, and the counting of the pulse rate, not to mention other indispensable helps in the every-day routine of medical practice. Nevertheless, the estimation of blood pressure has truly gained a prominent place in diagnostic technic; and the information which it has furnished has helped to awaken a tremendous interest in the large problem of arterial hypertension and related factors.