FROM THE HUMAN CHEST-WALL. 23 
A lever with a steel point was also in connection with the instrument, 
in such a way that when the tracing rested on the ledge the steel 
point produced scratches on the paper similar to those produced by the 
sphygmograph pen. 
_ By this means, the parts of the curve under consideration can be 
all projected on to one straight line, and their relative lengths 
measured with facility. Fig. X is a trace so prepared for measuring, 
and this arrangement is necessary on account of the sphygmograph 
lever moving in part of a circle instead of quite vertically. Further, 
to diminish inaccuracies in the watchwork movement, all the pulsa- 
tions on a trace were measured, and their average taken as the 
result. 
It was soon found that, with a given rapidity of pulse, the ratio 
of the first part of the heart’s revolution to the whole did not vary 
appreciably when traces were taken im any given position, but that 
when standing or sitting the first part was longer than when lying. 
Further, on comparing traces of different rapidities, it was found 
that the length of the first part varied very definitely, inversely as the 
rate; not so quickly, but as its square root: and the number of 
measurements that have been made seems to justify the law, that in 
health, the length of the first part of the heart’s beat varies, for a given 
position of the subject, inversely as the square root of the rapidity. 
This result differs from that of Donders,* who found that the 
length of the first part did not vary with different rates of heart’s 
action; but his means were much less efficient, he having to depend 
on the registration by the hand of the first and second cardiac sounds. 
All the facts on which the above law is supported are given in the 
accompanying table, in which they are thrown into the co-ordinate 
form, one co-ordinate, z, representing the rate of pulse, and the other, 
y, expressing the number of times the first part of the revolution is 
contained in the whole. The observations made while lying are repre- Pago 24. 
sented by a cross ( X ), when semi-recumbent these are encircled (@). 
The encircled dots (©) indicate that the position was sitting, and the 
standing ones are erect encircled crosses (). 
The simple dots are either from sitting or standing observations, 
but it is not certain which, as note was not taken at the time. 
For example, the measurement of two heart traces, one at 41 a 
minute while lying, and another at 141 when semi-recumbent, gave in 
the former case the ratio of the first part to the whole revolution 
1 : 34125, in the latter, 1 : 1-832; the length of the first part is found 
by multiplying the rate into the number of times the first part is 
* “On the Rhythm of the Sounds of the Heart.” By F.C. Donders. 1865. 
Translated into the “ Dublin Quarterly Journal of Medical Science,” Feb., 1868. 
