0 N THE SPHYGMOGEAPH, OR PULSE-RECORDER. 
131 
middle, and is free at the other end, to which a small pad is 
attached for pressing on the artery. Attached to this pulse- 
spring is a piece of brass work which carries a knife-edge just 
over the pad, and this is easily raised or lowered by a long 
screw with a milled head. The knife-edge is in contact with 
the recording lever near its axis, having a small steel plate to 
a a', Recording Lever ; b, Brass-work supporting the Knife-edge, d, and the Regu- 
lating Screw, t ; k, Pulse-pad. at end of JPulse-spring, i ; c, Arbor on which 
the Recording Lever rotates, close to whPh the Compressing-spring, y, acts ; 
p, Screw to regulate the strength of the Pulse-spring ; g r, Main Framework 
of the Instrument. — (From “ Handbook to the Physiological Laboratory.”) 
work upon. The lever is of the third kind, very light, and car- 
rying a thin steel pen or scratcher at its tip. From this 
description it may be seen that any movement, such as that 
of the pulse, raising the pulse-pad, raises the lever also, and 
the reverse. There is a screw arrangement for varying the 
amount of pressure exerted by the spring on the artery. 
The recording paper is fixed on a flat metal backing, which 
again is connected with a series of brass teeth, that catch in the 
wheel of the driving-wheel of the watch- 
work, running its whole length in ten 
seconds. 
The whole instrument is bound on the 
arm by a silk cord, that is attached to 
pegs in the side-lappets, fixed on the 
body of the instrument. 
Brequet now makes his sphygmograph 
on a slightly modified plan. Instead of 
the knife-edge and screw connecting the BREQUET s EACKW0RK MOm ' 
& FICATIOX OF THE SPHYGMO- 
recording lever with the pulse-pad, he graph.— (From “ Handbook 
has a simple screw attached to the spring to the Physiological Labo- 
in the same way that the blade is fixed rator Y- ) 
in a pocket-knife, so that it may be turned down flat or up at 
right angles. The worm of the screw bites in the teeth of a 
small wheel, which embraces the axis on which the recording 
lever works, and so makes the different parts of the instrument 
