138 
POPULAR SCIENCE REVIEW. 
Pulse Rate 
Number of times that the systolic length 
occurs in the whole length of the beat 
37 a minute . 
4*175 
49 
n 
3*51 
60 
ii 
3*09 
63 
ii 
2*93 
64 
ii 
2*91 
65 
ii 
2*9 
70 
ii 
2-775 
83 
ii 
2*45 
100 
ii 
2*16 
137 
ii 
1*7443 
From this table it is evident that the length of the systole 
must vary with the rapidity of the pulse, and with nothing else, 
it being constant for any given rate, or very nearly constant at 
rates which are very nearly the same. A large number of other 
measurements which I have made all help to verify the state- 
ment, that the length of the systole does not change in healthy 
persons when the pulses compared are of the same rapidity. 
But in pulses of different speeds the case is quite altered, as 
may be found from the above table ; in which the actual length 
of the systole in parts of a minute can be obtained by multiply- 
ing the numbers given in the second column by those repre- 
senting the corresponding pulse-rates in the first. The quan- 
tities thus obtained form the denominators of the fractions 
which represent the systolic length in parts of a minute, and 
they will be turned into decimals of a minute for facilitating 
comparison. As an instance, 1*7443 x 137 = 238*9691, and 
=0*0041841 of a minute. Again, 2*91 x 64 = 186*24, and 
Y 8 e-s -4 = 0*005369 of a minute. A little attention shows that 
the length of the systole does not vary as quickly as the beat, 
and that, by extracting the cube roots of the pulse-rates, num- 
bers are obtained which do vary in a corresponding manner, 
within the limits of experimental error. Thus, the cube root of 
64 is 4, and that of 137 is 5*155 : 
4 : 5*155:: 1 : 1*288 . . . 
and 41841 : 5369;: 1 : 1*283 . . . 
A similar arithmetical process applied to the other ratios in 
the same table will lead to the same result, namely, that the 
length of the systole , as indicated in the sphygmograp h trace 
from the radial artery does not vary when the pulse-rate is 
constant , but varies as the cube root of the rapidity of the 
cardiac action. 
This law, just stated, may be looked at in different lights as 
far as the manner in which the heart works and rests is con- 
cerned. Most of us always rest during the night and work in 
