THE PULSE. 525 



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 

 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. 498), 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 

 before entering the capillary regions, but as a result of dilatation in 

 the arteries of an organ the pulse may carry through and appear in 

 the veins, in which it may be shown, for instance, by the rhythmical 

 flow of blood from an opened vein. The term venous pulse, how- 

 ever, as generally used applies to an entirely different phenomenon, 

 — namely, to a pulse observed especially in the large veins (jugular) 

 near the heart. The pulse in this case is not due to a pressure wave 

 transmitted through the capillaries, but to pressure changes of 

 both a positive and negative character occurring in the heart or 

 the neighboring arteries and transmitted to the veins. The venous 

 pulse that has this origin may usually be seen and recorded in the 

 externa] (or internal) jugular. Under pathological conditions, espe- 

 cially when the flow through the right heart is more or less impeded, 

 it may be plainly apparent at a further distance from the heart and 

 may cause a noticeable pulsation of the liver, which is designated as 

 a liver pulse. The venous pulse curve has been much studied in 

 recent year's.* It is somewhat complicated and an explanation 

 of some of its details has not been agreed upon, but there can be no 

 doubt that if properly interpreted it throws much light upon 



* See Mackenzie, "The Study of the Pulse," 1902; also Lewis, in Hill's 

 "Further Advances in Physiology," New York, 1909. 



