ON TIIE SPHTGMOGEAPir, OE PULSE-EECOEDEE. 
135 
we are to make any use of our information. Dr. Burdon San- 
derson lias, by means of a simple apparatus attached to one 
end of the instrument, endeavoured to employ it as a hsemady- 
namometer or gauge, by means of which the pressure of the 
blood in the artery may be estimated. By adjusting the height 
of the pulse-pad^ at the same time that the pressure exerted 
by the spring is estimated on a graduated scale, he finds the 
degree of pressure required to 
give indications in the trace of 
excessive compression of the ar- 
tery against the bone, and so of 
the blood-pressure in the artery. 
There are several difficulties in 
the way, which make the results 
of comparatively little value, 
among which may be mentioned 
the differences in the elasticity 
of the skin of different indi- 
viduals, and the uncertainty at- 
tending the situation in which 
the vessel is compressed. 
In looking at sphygmograph 
traces from the pulses of dif- 
ferent rapidities, there is nothing j 
more striking than that the 
length of the interval between 
the commencement of the pri- dr- sanderson's method for” estimat- 
very considerably in different 
SPHYGMOGRAPH. 
y, Screw for regulating the distance of 
tracings, being nearly constant the instrument from the arm. — (From 
in each. In most works on “ Handbook to the Physiological Labo- 
Physiology it is stated that there rat0I 7-”) 
is a definite ratio between the length of systole and that of 
diastole. The subjoined table from “ Carpenter’s Principles of 
Human Physiology ” will serve as an example : — 
Auricles. 
Dilatation • 
Contraction . 
Ventricles. 
Contraction §. 
( First stage of Dilatation ) * 
(Second „ „ j 2 
No hint is ever given to show that these relations of the 
several parts of the heart-beat may vary, because before 
the introduction of the sphygmograph the means of carefully 
estimating them were not at hand. But as in the pulse 
trace it is possible, and not in the least difficult, to observe 
both the length of the systole and the diastole, every oppor- 
tunity is now afforded for their comparison. This must be done 
