The physiology and pathology of blood-pressure in man have excited the interest of a large number of workers for a great many years and without any apparent abatement. The contributions to the subject have been many; new forms of instruments are constantly being devised, new criteria for the determination of the pressures have developed, and extended observations on the pressures in physiological and pathological conditions have been published. In many places blood-pressure observations are now made as a matter of routine. In consequence of this activity, many persons who are not in a position to question the value of instruments, or to analyze critically the data they are said to afford, are called on to use instruments and to interpret results obtained therewith. It is, therefore, essential, in order to spare the time of the routine investigator and to prevent the appearance in the literature of numerous articles