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XXVI. On the Sources and Nature of the Powers on which the Circulation of 
the Blood depends. By A. P. W. Philip, M.D. F.R.S. L. E. 
Read June 16, 183J . 
It is remarkable that, notwithstanding the great importance of the circulation 
in the animal economy, the length of time which has elapsed since its discovery, 
and the constant attention it has obtained, there is hardly any department of 
physiology respecting which there appears to be greater uncertainty and con- 
trariety of opinion than the sources and the nature of the powers on which this 
function depends. I propose in the following paper, by comparing the prin- 
cipal facts on the subject, and by such additional experiments as seem still to 
be required, to endeavour to determine these points. Much has lately been 
written and many experiments have been made with this view, and it has 
become customary to look for the causes which support the circulation to 
other sources beside the powers of the heart and blood-vessels. 
It has been supposed that what has been called the resilience of the lungs, 
that is, their tendency to collapse, by relieving the external surface of the heart 
from some part of the pressure of the atmosphere, is a principal means of 
causing it to be distended with blood, the whole weight of the atmosphere 
acting on its internal surface through the medium of the blood which is thus 
propelled from the veins into its cavities ; and in this way it has been supposed 
that the motion of the blood through the whole of the venous part of the circu- 
lation is maintained. A similar effect has been ascribed to the act of inspi- 
ration, which it is evident must operate on the same principle ; and this opinion 
has even been sanctioned by the Report of a Committee of the Royal Academy 
of Sciences of Paris *, and in this country by men whose authority is deservedly 
high ; and the effect of these causes, it is asserted, is increased by the elastic 
power of the heart itself. 
* Report on Dr. Barry’s paper, by Baron Cuvier and Professor Dumeril. 
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