Although the collapsing pulse has, since the time of Corrigan, been one of the most characteristic features of aortic insufficiency, and although in its exaggerated form it furnishes the most typical of all pulse tracings, nevertheless one is struck by the frequency with which the sphygmograph produces a seemingly normal tracing in cases of perfectly definite aortic insufficiency where the sensation to the finger is that of a collapsing pulse. Usually it has been considered that such tracings are the result of instrumental defect or imperfect technic in making the tracings, and in a few cases they are ascribed to a simultaneous occurrence of aortic stenosis along with the insufficiency. The discrepancy between the sphygmographic tracings and the subjective notes is well exemplified in the examination of the records of patients observed in the Johns Hopkins Hospital during the past four years, in which the pulse was described