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32 MUTUAL RELATIONS OF THE APEX CARDIOGRAPH 
6.ON THE MUTUAL RELATIONS OF THE APEX CAR- 
DIOGRAPH AND RADIAL SPHYGMOGRAPH TRACE.* 
A vrstre to acquire an accurate knowledge of the relation born by 
the commencing contraction of the heart to the origin of the primary 
rise in the pulse at the wrist, led the author to construct an instrument 
which has enabled him to determine, with considerable accuracy, the 
mutual relation of these two points, and to demonstrate one or two 
unexpected results, not altogether without interest. 
[Here follows an account of the cardio-sphygmograph described in 
the preceding paper.—Ep. | . 
All the observations were made on the same subject, aged 24, in 
good health. They were all made in the sitting posture, as the appa- 
ratus could then be held more firmly, or rested on the arm of a chair. 
To facilitate description, the following terms and symbols will be 
employed with regard to pulse-traces. 
1. The rapidity of the pulse is symbolically represented by z. 
2. The first cardiac interval is that which oceurs between the com- 
mencement of the systolic rise and the point of closure of the aortic 
valve, in cardiograph traces. The number of times that this interval 
is contained in its component beat is represented by y; and the law as 
to its length, published spatiale eb will be assumed. It may be stated 
thus :-— 
vy = 20/2. 
8. The first arterial interval is that which occurs between the com- 
mencement of the primary rise and the termination of the major fall 
in arterial sphygmograph traces. The number of times that this 
interval is contained in its component beat is represented by y'; and 
the law as to its length at the radial artery, which is alone considered 
in this communication, published in the “ Proceedings of the Royal 
Society ” (No. 120, 1870),t will be assumed ; it may be thus stated :— 
ay’ = 47 8/2. 
4. The first cardio-arterial interval is that which occurs between 
the commencement of the systolic rise in the cardiograph trace and 
the origin of the main rise in the sphygmograph trace. The number 
of times that this interval is contained in its component beat is repre- 
sented by z. 
5. The conjugate cardio-arterial interval is that portion of the first 
* “Proceedings of the Royal Society,” XIX. pp. 318-24. Read Feb. 23, 1871. 
+ “ Journal of Anatomy and Physiology,” Cambridge, V. Nov. 1870. (Supra, 
p. 18.) t Supra, p. 14. ’ 
