Page 140. 
Page 141. 
78 ON POINTS CONNECTED WITH THE 
12, ON SOME POINTS CONNECTED WITH THE CIR- 
CULATION OF THE BLOOD, ARRIVED AT FROM 
A STUDY OF THE SPHYGMOGRAPH-TRACE*+ — 
(Pl. III.) 
Sivcz my first communication to the Royal Society, “On the rela- 
tive Duration of the Component Parts of the Radial Sphygmograph- 
Trace in Health” (“Proceedings of the Royal Society,” XVIII. 
p. 351+), it has not been my good fortune to find any similar observa- 
tions by other physiologists, either in favour of or in opposition to my 
statements. From that time my attention has been continually 
directed to similar phenomena; and the employment of similar 
methods has led to results which seem to have an important bearing 
on the problem of the action of the heart. It is evident that a 
thorough knowledge of the nature of the pulse in the arteries, when 
combined with that acquaintance with the anatomical mechanism of 
the heart and arteries that can be arrived at from post mortem examina- 
tion, is sufficient basis for a fairly thorough study of the circulation of 
the blood. It has been my endeavour, by the employment of the 
sphygmograph as constructed by M. Marey, to obtain an amount of 
information from the curves which it produces sufficient to generalise 
on the nature of the cardiac action in some of its details which have 
not as yet attracted attention. The results will be stated in the form 
of propositions. 
Prop. I. The length of the interval between the commencement of 
the ventricular systole at the heart and the closure of the aortic valve 
does not vary when the pulse-rate is constant, and varies as the square 
root of the length of the pulse-beat—being found from the equation 
ay = 20 /x, where « = the pulse-rate, and y = the ratio borne by 
the above-named part to the whole beat. 
This law, in a somewhat modified form, was enunciated by myself 
in 4 paper published in the “Journal of Anatomy and Physiology” 
(V. p. 17),t where the peculiarities of the curves taken in the lying 
posture misled me as to the point of commencement of the ventricular 
systole, and led me to state that posture had an effect on the duration 
of the systole. Such, however, is not the case; for, while lying, the 
weight of the heart is apparently sufficiently great to neutralise the 
* “ Proceedings of the Royal Society,” XXIII. 1875, pp. 140-51, Pl. 5. Read 
April 23, 1874. An abstract of this paper is published, loc. cit., XXII. pp. 291-3. 
+ Supra, p. 14. t Supra, p. 18. 
