492 
DR. PHILIP ON THE POWERS ON WHICH 
state of relaxation. Besides, the auricles possess little or no elasticity ; and 
whatever the elasticity of the ventricles may be, it can have no effect on the 
blood in the veins, because they receive their blood from the auricles which 
are contracting during the diastole of the ventricles. To these statements it 
may be added, that in many of the inferior animals the foregoing supposed 
causes of the venous part of the circulation evidently have no existence, and 
that, with the exception of the elasticity of the heart, they have no existence in 
the fetal state in any. 
We have just seen from direct experiment, that the circulation of the blood 
goes on as usual when all these causes have wholly ceased to operate. 
I shall now take a rapid view of the facts which, as far as I am capable of 
judging, leave no room of doubt respecting the sources of the power on which 
this function depends. 
It is so evident to those in the least acquainted with the animal economy 
that the contractile power of the heart is one of the chief of these sources, that 
it would be superfluous to enumerate the proofs of it; yet even this position has 
been denied, and that by a writer of no mean abilities. The opposite error, 
however, is the more common ; and not a few have ascribed, and even still do 
ascribe, the motion of the blood throughout the whole course of circulation to 
the contractile power of the heart alone, although it would not be difficult to 
prove that to drive the blood through one set of capillary vessels, and still more 
through two or three sets of such vessels, — for in man himself, in one important 
part of the circulation, it is carried through two, and in some animals through 
three, sets of capillaries before it returns to the heart, — I say it would not be 
difficult to prove that to drive it through one set of capillaries, at the rate at 
which the blood is known to move, would require a force capable of bursting 
any of the vessels. But here, as in the former instance, it is better to appeal 
to the evidence of direct facts than to any train of reasoning; and there is no 
want of such facts to determine the point before us, some of which I formerly 
had the honour to lay before the Society, and others are stated in my Treatise 
on the Vital Functions. The most decisive is, that the motion of the blood in 
the capillaries continues long after the heart has ceased to beat and the animal 
in the common acceptation of the term is dead, even in the warm-blooded 
animal, for an hour and a half or two hours, and it is not for some time sen- 
