It is well at times to free our minds from the fixity of things as they are and try to see an object in its actual relationship to the complete scheme of things to which that object belongs. A true perspective thus gained will occasionally save us from getting too far from the main road of travel and from going astray. Because arterial hypertension has been so widely studied, even to the point of having quite a number of books written on the subject, arterial hypotension has likewise been trotted into the medical arena, to have its action and values carefully rated. Whatever advance has come to medicine through the study of arterial tension, this study was only made possible by the perfected sphygmomanometer. Blood pressure instruments, as well as blood pressure studies, have rendered a signal service to medicine; and we who have used them, each model in its