36 MUTUAL RELATIONS OF THE APEX CARDIOGRAPH. 
small intervals into one another with precision; but by practice a very 
fair estimate can be made of their value, and in all cases they seem to 
agree with theoretical requirement. The close accordance of the 
results obtained by this method in very slow pulses, and the calculated 
results arrived at from facts relating only to quicker ones, tends 
strongly to establish the correctness of the law given with regard to 
them. . 
In Table IV the lengths, in parts of a minute, of the different 
intervals referred to in this communication, are given as calculated 
from the equations on which they have been shown to depend. With 
regard to the second cardio-arterial interval, a reference to Column VII 
will show that it varies very slightly within the range of the heart’s 
action, not being 4 longer in a pulse of 36 than in a pulse of 169 ina 
minute. 
Page 324. Taste IV. 
I. II. III. TV; V. VI. Vit. 
Length of 
Length of | Length of | second 
Rapi- | Length of Perper Pires oat first cardio- | conjugate | cardio- 
dity of pulse-beat, jbooed ats ct arterial | cardio-arte-| arterial 
y in parts of Peqtcne of re alt ’ € interval, in | rial interval.| interval, in 
pulse. | a minute. | RRA ee wis parts of | in parts of | parts ofa 
* | @minute. | a minute. | a minute. | minute. 
36 | 027 ‘0083033 | 006428 0042735 | °0040298 | ‘00239821 
49 | *020408 | :00714286 | -005813 003663 00347986 | °00233342 
64 015625 "00625 005319 "003205 “0030449 00227425 
81 0123457 | *005 “00491356 | -0028474 | ‘0027081 00220546 
100 “01 "005 | 004.6234 *0025641 *0024359 00218745 
121 | 0082645 | -0045_ “004299 002331 00221445 | +0020847 
144, “00694, “00416 “004.0486 *0021365 *0020301 “0020185 
169 | 005917 | -003846 ‘0038485 | -0019704 | 0018756 | ‘0019729 
In conclusion, the following are the results that have been arrived 
at by the use of the above cardio-sphygmograph :— 
1. The first cardio-arterial interval varies inversely as the square 
root of the pulse-rate. 
2. The conjugate cardio-arterial interval varies inversely as the 
square root of the pulse-rate. 
3. The second cardio-arterial interval varies very little with differ- 
ent pulse-rates, but is slightly longer in slower pulses. 
4. The depth of the notch in the first arterial interval of the 
sphygmograph trace occurs at the moment of closure of the aortic 
valve. 
5. There is no definite indication in the sphygmograph trace of 
the moment at which the cardiac systolé commences. 
