ON THE SPIIYGMOGRAPH, OH PULSE-RECORDER. 137 
supporting, portion of the watchwork does to the axis of the 
recording lever. A stout needle (d) is then threaded with 
cotton or silk (e), of which the two ends are made to tie round 
the screw above mentioned, at 5J inches or so from its eye, 
according to the length of the recording lever. A small length 
of string (e) is also attached at one end to the same screw, and 
knotted (g) at 5 J inches from it ; the needle-point is then 
made to run into the knot a short distance, and project slightly 
beyond it. By this arrangement, if the thread and string are 
put on the stretch, by the finger placed between them against 
the needle, the point of the needle can be readily made to draw 
a circle similar to that formed by the recording lever. The 
tracing then being placed along the ridge on the board, the 
necessary curves are made on it from the points which it is 
desired to project. 
By means of a small ordinary spring-bow, with a screw-nut 
to regulate the distances between its points, great precision in 
measuring can be arrived at with a little practice. 
It is best to measure the length of each beat in the trace, 
and striking the average of them all, to consider that as the 
actual ratio desired. By this means the complication intro- 
duced by the effects of respiration is much reduced, and the 
inequalities in the movement of the watchwork are in great 
measure neutralised. For instance, in a pulse beating forty- 
four times a minute the following were the actual numbers 
obtained : — 
3-8 3-8 
3-775 3-8 25 : with the average of 3*8. 
Again, in a pulse beating 137 times a minute the following 
were also the numbers, in which the effects of respiration are 
clearly marked : — 
1-8 1-775 1-72*5 1-775 1-75 
1-725 1-725 1-775 1-675 1-728 
1-725 1-7 ,1-8 1*75 with an average of 1*7443. 
It will not require a long experience in sphygmograpkic 
measurement to convince the student that it is in quick pulses 
that the systole is proportionately the longer, and in slow 
pulses the shorter, inspection alone putting that beyond a 
doubt. But when observations become more numerous, fresh 
facts become apparent. The following table gives the results 
obtained from a series of measurements in which the rapidity 
of the pulse was carefully observed, and the number of times 
that the systolic length was contained in the whole beat was 
recorded : — 
