Page 148, 
86 ON POINTS CONNECTED WITH THE 
that it will write on the same recording-paper as the first; but its 
position is reversed. The accompanying sketch (fig. 3) will show 
this point, it representing a side view of the ordinary knife-edge 
lever upside down—that is, with the surface (s) on which the knife- 
edge ought to slide uppermost. the object of this arrangement will 
be seen immediately. 
The second sphygmograph has the jes wieeke removed, as well as 
the brasswork which is fastened to the spring that presses on the 
pulse, to the end of which a small wire loop is soldered. In addition, 
a small piece of wood is screwed into the nearer of the two holes by 
which the watchwork was fixed, in such a way that it can be made to 
revolve with difficulty. The two instruments are fastened together by 
means of a screw and nut in the foot-sphygmograph, which bind a 
brass plate in that for the wrist. This screw is fixed on a plate of 
brass which is attached to the end of the instrument furthest from the 
watchwork in the manner shown in the figure. The brass plate in the 
other sphygmograph, which it binds, is fixed on the side of the body 
of the instrument close to the arbor of the lever. The exact position 
of these additional pieces of brasswork has to be determined by the 
direction that a silk cord takes when, fixed at one end to the arbor- 
end of the inverted lever mentioned above, it is threaded through the 
loop on the tip of the spring of the wrist-sphygmograph. This cord 
has to be parallel to the sides of the ankle-sphygmograph, when the 
two instruments are fastened together with the nut at right angles to 
one another. 
On commencing to take a double trace the nut is unscrewed, and 
the two instruments are separated from one another. The wrist- 
sphygmograph is then bound, as usual, on the rightarm. The silk 
cord attached to the arbor-end of the wrist-pulse lever (the upper one 
in the ankle-sphygmograph) is then threaded through the loop at the 
tip of the wrist-spring, and the binding-screw to fix the two instru- 
ments is passed into the hole in the plate of the wrist-sphygmograph 
made to receive it; after which, the nut being screwed fast down, the 
two sphygmographs form a single mass. The silk cord is then carried 
round the piece of wood at the watchwork end of the wrist-sphygmo- 
graph, and, after being slightly tightened, is fixed in a groove on its 
side. The whole is now ready for commencing the trace. To do this 
the ankle instrument (with that for the wrist attached to it and to the 
arm) is placed over the left foot, which has to rest on the right knee, 
parallel to the direction of the leg, with the watchwork towards the 
body. The recording-paper is placed in position; the silk thread is 
tightened by slightly turning the wooden peg to which it is fixed, and 
the wrist-lever is made to pulsate by it towards the upper part of the 
recording-paper. The ankle-sphygmograph, held by its watchwork 
