942 



PHYSIOLOGY 



photographic plate or paper. The advantage of this optical method of registration is 

 that the magnification can be increased to any extent without altering the mass moved. 

 The * figure of merit ' of this manometer, i. e. its own period of vibration, when filled 

 with fluid, is about 250 per second with a thick membrane, so that it can record with 

 perfect accuracy all such rapid changes of pressure as may occur even in the left ventricle. 



FIG. 408. Endocardiac pressure (racings, taken with Piper's manometer. 



A, Simultaneous tracings from left ventricle and left auriele. To bo road from left 

 to right. B and C taken from left \entricle, T at a taster rate of recording surface 

 than l>. To be road from ri^ht to left. Kj = closure of A. V. valves; Sj, opening 

 of aortic valves; S 2 , elastic oscillation or wave; Kj, opening of A.V. valves. 



