THE PULSE. 



521 



from this figure that the artery dilates rapidly and then falls more 

 slowly, but it must be borne in mind that the very pointed apex 

 of the wave recorded by this form of sphygmograph is due to 

 an instrumental error, namely, the "fling" of the lever caused by the 

 sudden expansion of the artery. A more accurate record of the 

 radial pulse is shown in Fig. 213. The ascending portion of the 



Fig. 212. — Sphygmogram from the radial artery, Dudgeon sphygmograph: D, The dicrotic 

 wave; P, the predicrotic wave. 



wave is spoken of as the anacrotic limb, the descending, as the 

 catacrotic limb. Under usual conditions the anacrotic hmb is 

 smooth — that is, shows no secondary waves — while the catacrotic 

 limb shows one or more secondary waves, which are spoken of in 

 general as the catacrotic waves. The most constant of these latter 

 waves occurs usually approximately at the middle of the descent 

 (D) and is designated as the dicrotic wave. A less conspicuous 

 wave between it and the apex of the pulse wave is known usually 

 as the predicrotic ivave, P, while the wave or waves following the 

 dicrotic are designated as postdicrotic. These catacrotic waves are 

 too small, under normal conditions, to be felt by the finger. Under 



Fig. 21.3.— Record of the radial pulse taken with a Frank -Potter sphygmograph. — i After Pe«er.) 



certain abnormal conditions, however, which cause a low blood- 

 pressure without marked diminution in the heart beat, the dicrotic 

 wave is emphasized and may be detected by the finger. A pulse of 

 this kind is known as a dicrotic pulse. In each pulse wave we may 

 distinguish a systolic and a diastohc phase; the former, making due 

 allowance for transmission, corresponds with the time during which 



