SPHYGMOGRAM 



2 39 



any desired height to which the lever is adapted by tightening or slackening the spring ; 

 the tap, c, is then closed. The pressure within the box acts in all directions, and is 

 correctly indicated by the manometer. 



To manometer. 



FIG. 197. Diagrammatic Sectional Representation of the Sphygmometer. a, Box 

 by which the portion of the artery is covered; &, thin- walled india-rubber bag filled with 

 water, and communicating through tap, c, with the manometer and thick- walled rubber bag, 

 h; d, piston connected by rod, e, with recording lever,/; g, spiral spring, attached to axis of 

 lever, and by which the pressure in b, against the piston, d, is counterbalanced; k, skin and 

 subcutaneous tissue; m, end of radius seen in section; n, radial artery seen in section. 

 (Roy and Adami.) 



Sphygrnogram. The tracing of the pulse obtained by the use of the 

 sphygmograph, called a sphymogram, differs somewhat according to the artery 

 from which it is taken, but its general characters are much the same in all 

 cases. It consists of a sudden upstroke, or anacrotic limb, figure 198, A, 

 which is somewhat higher and more abrupt in the pulse of the carotid and of 

 other arteries near the heart than in the radial and other arteries more re- 

 mote; and a gradual decline or catacrotic limb, P, less abrupt, and taking a 

 longer time than A. It is seldom, however, that the decline is an uninter- 

 rupted fall; it is usually marked about half-way by a distinct notch, C-D 

 the dicrotic notch, followed immediately by a second more or less marked 

 ascent of the lever called the dicrotic wave, D. Not infrequently there is 

 also at the beginning of the descent a slight wave previous to the dicrotic 

 notch; this is called the pre-dicrotic wave, and in addition there may be one 

 or more slight waves after the dicrotic, called post-dicrotic, E. The inter- 

 ruptions in the downstroke are called the catacrotic waves to distinguish 

 them from an interruption in the upstroke, called the anacrotic wave, which 

 is sometimes met with. 



