48 



lever to the apex by means of a small clip, seeing that the thread 

 18 vertical (fig. 15). Adjust the lever (a) by its height on the 

 stand, (6) by the spiral spring, so that each heart beat causes 

 the largest range of movement. Then bring the glass point of 

 the lever lightly against the drum ; start the drum at a very 

 slow rate, and take a record of several cardiac cycles. Remove 

 the lever and put a time record in tenths of a second under 

 the trace. Fix the tracing. 



kast f 



Fia. 15. Arrangement of Frogboard. 



When fixed determine 



(1) the rate of recurrence of the cardiac cycle, i.e. the rate 

 of the heart ; 



(2) the duration of the ventricular systole ; 



(3) the duration of the auricular systole, if this is marked 

 upon the trace. 



