Page 23. 
58 THE LAW WHICH REGULATES 
The great interest attaching to these figures is that, when with the 
diaspasis equal to ‘00183 of a minute, the ratio of the systole to the 
diastole is enquired into, it is found that there is a very simple rela- 
tion between them, and that after subtracting this diaspasis of con- 
stant length, there remains the systolic varying as the square root of 
the diastolic period, and with no other diastolic length is so simple a 
ratio obtainable, which is all-important, because it will be seen that 
the systole must depend directly on the previous diastole. 
Next, considering the systole itself; the fact above demonstrated, 
that its length does not depend on the blood pressure, is extremely 
important, and can only be explained by assuming that when the 
pressure rises, the circulation through the coronary vessels increases 
to a sufficient extent to enable the heart to get through the extra work 
it has to perform without altering the duration of its action, or, in 
more precise terms, the nutrition of the walls of the heart must vary 
directly as the blood pressure in the aorta. 
But the systolic length varies as the square root of the diastolic, 
in other words, the longer the time of nutrition of the heart, the 
longer the systole. This at first sight seems an anomaly, but the 
theory that the pulse-rate depends on the fall in tension only, presents 
a most complete explanation, and so throws great light on cardiac 
action in general. 
Consider the heart as a pump working against a certain pressure, 
and filling an elastic reservoir with a certain resistance to the outflow 
of its contents. Varying the pressure has been shown to have no 
effect on the lengths of the different parts of the pulsation for the 
reasons given above; and it has next to be considered how it is that 
varying the resistance changes the lengths of the elements of the 
revolution. This pump, directly its muscular fibres begin to contract, 
exerts its full pressure, for there is nothing to prevent it doing so. 
But during the previous diastole it was supplied by blood at a certain 
definite pressure and for a definite time, both of which factors limit 
the force of the systole. Consequently, the ventricles produce directly 
their full systolic pressure, and maintain that pressure until they are 
empty. But it is evident that the time necessary for emptying them 
of a definite amount of blood under these conditions must depend on 
the rapidity of the flow from the capillaries, for when the flow is 
halved the systolic time must be doubled, if no other force come into 
play ; in other words the length of cardiac systole is a function of the 
arterial resistance; and the pulse-rate has also been shown to be a 
function of the same, upon the fall of tension theory. 
It has been proved that the systole varies as the square root of the 
diastole, not directly with it, as might be supposed. This clearly 
shows that the time of diastole influences the length of the systole 
