THE PULSE. 531 



is regular or irregular. By the same means one can determine 

 whether the pulse is large (pulsus magnus) or small (pulsus par- 

 vus), whether the wave rises and falls rapidly (pulsus celer) as hap- 

 pens in the case of insufficiency of the aortic valves, or whether in 

 one phase or the other it is more prolonged than normal (pulsus tar- 

 dus). It seems obvious, however, that a more satisfactory conclu- 

 sion may be reached in all such cases by obtaining a sphygmographic 

 record, although, as previously intimated, the details of such tracings 

 as obtained from most forms of sphygmographs have come under 

 suspicion on account of instrumental errors in the recording ap- 

 paratus. By mere pressure upon the artery one can deter- 

 mine also approximately whether the blood-pressure is high or 

 low by estimating the force with which the wave presses upon 



Fig. 216. Sphygmograms illustrating the effect of variations in blood-pressure, partic- 

 ularly upon the position of the dicrotic wave and notch : n, The dicrotic notch ; d, the 

 dicrotic wave. A, Sphygmogram while blood-pressure was relatively low. B, Sphygmo- 

 gram with higher blood-pressure. (Mackenzie.) 



the fingers, or the pressure necessary to occlude the artery. A 

 similar inference may be drawn from the character of the sphyg- 

 mogram, and especially from the relative size and position of the 

 dicrotic wave. When this latter wave falls at or near the base line 

 of the curve it indicates a low arterial pressure, since under these 

 circumstances the artery collapses readily after its first systolic 

 expansion (see Fig. 216). Since the introduction of the sphyg- 

 momanometer (p. 503), however, it seems evident that this instru- 

 ment must be appealed to whenever the determination of blood- 

 pressure is a matter of importance. 



Venous Pulse. Under usual conditions the pulse wave is lost 



