THE PULSE. 493 



auriculo- ventricular valves and their protrusion to some extent into the 

 auricular cavity. This wave occurs, therefore, at the very beginning of the 

 systole. Wave t, corresponding with Mackenzie's wave v, occurs, on the contrary, 

 at the end of systole and is therefore designated by Bard as telesystolic. He 

 attributes this wave to the fact that during ventricular systole the base of the 

 heart is pulled toward the apex, thus enlarging the auricular cavity and exerting 

 an aspiratory effect on the venous flow. The cessation of this aspiratory effect 

 at the end of the systole and when the auricle is already fully distended gives 

 a sudden check to the flow of venous blood which causes the wave. The 

 negative wave, Ro, between S and t, corresponds to the diastolic expansion 

 of the auricles, while the larger depression (Rv) corresponds to the diastolic 

 expansion of the ventricles. In addition to the three waves described, pre- 

 systolic (p), systolic (s), and telesystolic (/), Bard describes a small wave 

 between p ami *, which he designates as intersystolic (?'), and another, occurring 

 in early diastole (d wave), which follows immediately after the t wave. 



