64 



fall, the author concludes, that they are in the ratio of the areas of 

 the orifices, independently of their shape; and nearly as the square 

 roots of the heights. In pipes bent at various angles the retarda- 

 tion occasioned by the flexure was not in proportion to their num- 

 ber. 



A paper was read, " 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. & Ed. 



In the first part of this paper the author discusses the opinions 

 which ascribe the powers that maintain the circulation in the veins 

 to the elasticity of the heart, the resilience of the lungs, and the 

 dilatation of the thoracic cavity in the act of inspiration. He shows 

 experimentally that the circulation continues unimpaired when all 

 those causes have ceased to operate; and that the very structure of 

 the veins, the coats of which are so pliable as to collapse by their 

 own weight, when empty, renders it impossible that the motion of 

 the blood could be maintained in them by any cause corresponding 

 to a power of suction in the heart. 



The latter part of the paper is occupied by an inquiry into the 

 sources and nature of the powers which really support the circula- 

 tion of the blood. The capillaries, he observes, maintain the mo- 

 tion of their blood long after the heart has ceased to beat • this 

 motion not being immediately affected even by the entire removal 

 of the heart ; but being accelerated, retarded, or arrested, according 

 as the action of the capillaries is increased, impaired, or destroyed, 

 by agents of which the operation is wholly confined to the vessels 

 themselves. As the destruction of the heart does not immediately 

 influence the motion of the blood in the capillaries, so the action of 

 this organ, when in full vigour, can produce no motion of the blood in 

 the capillaries, when these vessels are themselves deprived of power. 

 Experiments are related with the view of proving that the arteries 

 and veins, and more particularly the latter, are also capable of car- 

 rying on the blood they contain, even in opposition to the force of 

 gravitation, with the greatest ease, and without the aid of any ex- 

 traneous power. With regard to the nature of the power exerted 

 by the blood-vessels, the author shows that the capillaries are as 

 readily influenced by stimulants and by sedatives, as the heart itself ; 

 and that the arteries and veins may also be made to obey the action 

 of stimulants ; and further, that the power of the vessels bears the 

 same relation to the nervous system as that of the heart, which is 

 peculiar, and very different from the relation subsisting between 

 that system and the muscles of voluntary motion. From the whole 

 of the facts and experiments stated in this paper, the author de- 

 duces the conclusions, that the circulation is maintained by the 

 combined power of the heart and blood-vessels, and that the power 

 of both is a muscular power. 



A paper was read, entitled, " A critical and experimental In- 

 quiry into the Relations subsisting between Nerve and Muscle." By 



