Identifier: handbookofphysio00bake (find matches)
Title: Hand-book of physiology
Year: 1892 (1890s)
Authors: Baker, W. Morrant, (William Morrant), 1839-1896 Harris, Vincent Dormer Kirkes, William Senhouse, 1823-1864. Hand-book of physiology. 13th ed
Subjects: Physiology Human physiology
Publisher: London : John Murray
Contributing Library: Francis A. Countway Library of Medicine
Digitizing Sponsor: Open Knowledge Commons and Harvard Medical School

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pstroke is usually single. In thiscase the percussion-impulse is not sufficiently strong to jerk upthe lever and produce an effect distinct from that of the tidalwave which immediately follows it, and which continues andcompletes the distension. In cases of feeble arterial tension,however, the percussion-impulse may be traced by the sphygmo-graph, not only in the carotid pulse, but also to a less extent inthe radial. The interruptions in the downstroke are called the katacroticwaves, to distinguish them from an interruption in the upstroke,called the anacrotic wave, occasionally met with in cases inwhich the pre-dicrotic or tidal wave is higher than the percussionwave. There is considerable difference of opinion both as to whetherthe dicrotic wave is present in health, and also as to its cause.The balance of opinion, however, appears to be in favour ofthe belief that the dicrotic wave to a greater or lesser degree ispresent in health • in certain conditions not necessarily diseased,
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Fig. 186.—Anacrotic pulse from a case of aortic aneurism, a, anacrotic wave, (or per-cussion wave; b, tidal or pre-dicrotic wave, continued rise in tension (or higher tidalwave). it becomes so marked as to be quite plain to the unaided finger.Such a pulse is called dicrotic. Sometimes the dicrotic riseexceeds the initial upstroke, and the pulse is then called hyper-dicrotic. As to the cause of dicrotism, one opinion (i) is that it is due toa recovery of pressure during the elastic recoil, in consequence ofa rebound from the periphery. It may indeed be produced on aschema by obstructing the tube at a little distance beyond thespot where the sphygmograph is placed. Against this view, how-ever, is the fact that the notch appears at about the same point in 224 CIECULATION OF THE BLOOD. (CH. VI. the downstroke in tracings from the carotid as from the radial,and not first in the radial tracing, as it should do, if this theorywas correct, since that artery is nearer the periphery than the

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