ON THE FUNCTIONS OF THE HEART AND ARTERIES. IgS 



the neighbouring vessels. But since it seenos probable, 

 that the minute arteries are more afi'ected by distension than 

 the veins, there is reason in general to expect a more speedy 

 and efficacious relief in infiammations, from opening an Aneriotomy, 

 artery than a vein : this operation, however, can seldom be 

 performed without material inconvenience; but it is proba- 

 bly for a similar reason, that greater benefit is often expe- 

 rienced from withdrawing a small portion of blood by means 

 of cupping or of leeches, than a much larger quantity by Cupping and 

 venesection, since both the former modes of bleeding tend leeches. 

 to relieve the arteries, as immediately as the veins, from 

 that distension, which appears to constitute the most essen- 

 tial characteristic of inflammation. In a case of hemorrhage Use of iox- 

 from one of the sinuses of the brain, a very judicious phy- |l^^'rhage.*^*' 

 sician lately prescribed the digitalis : if the effect of this 

 medicine tends principally to diminish the action of the 

 heart, as is commonly supposed, it was more likely to be 

 injurious than beneficial, since a venous plethora must be 

 increased by the inactivity of the heart; but if the digitalis 

 diminishes the general tension of the arteries, in a greater 

 proportion than it affects the motion of the heart, it may 

 possibly be advantageous in venous hemorrhages. We 

 have, however, no sufficient authority for believing, that it 

 has any such effect on the arterial system in general. 



Although the arguments, which 1 have advanced, appear ^^^J;"^^^^ ^^^^ 

 to me sufficient to prove, that, in the ordinary state of the arteries have 

 circulation, the muscular powers of the arteries ^^^'^ very |jj^le effect on 

 little effect in propelhng the blood, yet I neither expect circulation. 

 nor desire, that the prevailing opinion should at once be 

 universally abandoned. I wish, however, to protest once 

 more against a hasty rejection of my theory, from a super- 

 ficial consideration of cases, like that which has been re- 

 lated by Dr. Clarke ; and to observe again, that the objec- 

 tions, which 1 have adduced, against the operation of the 

 muscular powers of the arteries in the ordinary circulation, 

 not being applicable to these cases, they are % no means 

 weakened by any inferences which can be drawn from them. 



IV. 



