242 CIRCULATION. 



Inscribe a 1/10 second trace below them. 



Take a record for one revolution of the drum only at a 

 time. 



JSTote carefully the relative position of the dicrotic wave in 

 the pulse curve to the end of the systolic plateau of the 

 cardiogram, and estimate the time interval by which they are 

 -separated. This interval corresponds to the time which the 

 pulse wave has taken to travel from the aortic valves to the 

 wrist. Measure approximately this distance in centimetres by 

 means of a tape measure, and from these data calculate the 

 rate of propagation of the pulse wave per second. 



The length of the pulse wave can be determined by multi- 

 plying its rate of propagation per second by the time which 

 it takes to pass a given point, e.g., the time which it takes to 

 pass the point at the wrist to which the sphygmograph has 

 been applied. 



21 The pulse tracing, with Dudgeon's sphygmograph. 



Place the wrist of the subject in position upon the pad. 



Mark the point over the radial where the pulse is most 

 distinctly felt, and rest the button of the spring of the 

 sphygmograph upon the chosen point, and secure in position 

 with the tape. 



Adjust the pressure of the button upon the artery by 

 means of the eccentric until a maximal excursion of the 

 recorder is obtained. 



Wind up the clockwork, insert a strip of smoked paper 

 between the guide wheels, and let the paper travel past the 

 recording point as soon as the latter moves regularly. 



Examine the tracing : The first part of the curve is a 

 main upstroke, devoid of secondary oscillations, upon the 

 descent is the dicrotic wave, preceded by the corresponding 

 notch. 



