134 



CHARACTERS OF A PULSE-CtJRVE. 



as in Marey's apparatus, which greatly facilitates the measuring of 

 the curves. (Fig. 53.) 



Other sphygmographs are used, both in this country and abroad, including that 

 of Sommerbrodt, which is a complicated form of Marey's sphygmograph, and 

 those of Pond and Mach. In choosing a sphygmograph, that instrument is to be 

 preferred which yields a curve corresponding most closely with the variations of 



the pressure within the artery, in 

 which the resistance of the instrument 

 is small, which gives the largest curve, 

 and in which the part in contact with 

 the artery is not greatly displaced 

 from its position of equilibrium 

 (Mach). 



Characters of a Pulse-Curve. 



In every pulse-curve SPHYGMO 

 GRAM or ARTERIOGRAM we can 

 distinguish the ascending part 

 (ascent) of the curve, the apex, 

 and the descending part (descent). 

 Secondary elevations scarcely 

 ever occur in the ascent, which 

 is usually represented by a 

 straight line, while they occur 

 constantly in the descent. Such 

 elevations occurring in the de- 

 scent are called catacrotic, and 

 those in the ascent, anacrotic 

 (Landois). When the recoil 

 elevation or dicrotic wave occurs 

 in a well-marked form in the 

 descent, the pulse is said to be 

 dicrotic, and when it occurs twice, 

 tricrotic. 



Measuring Pulse-Curves. If the 



smoked surface on which the tracing 

 is inscribed is moved at a uniform 

 rate by means of the clock-work, 

 then the height and length of the 

 curve are measured by means of an 

 ordinary rule. If we know the rate 

 at which the paper was moved, then 

 it is easy to calculate the duration of 

 any event in the curve. For exact 

 observation a low-power microscope 

 with a micrometer in the eye-piece 

 should be used. 



Fig. 54. 



Pulse-curves of the carotid, radial, and 

 posterial tibial arteries of a healthy 

 student, obtained by Landois' angio- 

 graph writing upon a plate attached 

 to a vibrating tuning-fork. Each 

 double vibration corresponds to 

 0-01613 sec. 



should be used. 

 For the method of smoking the paper and fixing the tracings see p, 130 



