The clinical aspects of arterial blood pressure must be studied from a practical standpoint and in a thorough and systematic way, if, in the treatment of diseases, we are to derive any real benefit from such study. We must study arterial pressure not merely by digital estimation, but also by such an apparatus as will indicate the smallest variations in blood pressure to a nicety and with certain reliance. Such an apparatus we now fortunately possess in the Sphygmometer, of which there are several varieties on the market. Of these undoubtedly the most reliable, as well as the most convenient, is Dr. C. J. Martin's modification of the Riva-Rocci Sphygometer. This instrument is quite simple and accurate.