14 On the Heart and Blood 



an experiment to prove the contrary : An artery having 

 been exposed, is opened longitudinally, and a reed or 

 other pervious tube, by which the blood is prevented 

 from being lost, and the wound is closed, is inserted 

 into the vessel through the opening. " So long," he 

 says, " as things are thus arranged, the whole artery 

 will pulsate; but if you now throw a ligature about the 

 vessel and tightly compress its tunics over the tube, you 

 will no longer see the artery beating beyond the ligature." 

 I have never performed this experiment of Galen's, nor 

 do I think that it could very well be performed in the 

 living body, on account of the profuse flow of blood 

 that would take place from the vessel which was 

 operated on ; neither would the tube effectually close 

 the wound in the vessel without a ligature; and I cannot 

 doubt but that the blood would be found to flow out 

 between the tube and the vessel. Still Galen appears 

 by this experiment to prove both that the pulsative 

 faculty extends from the heart by the walls of the 

 arteries, and that the arteries, whilst they dilate, are 

 filled by that pulsific force, because they expand like 

 bellows, and do not dilate because they are filled like 

 skins. But the contrary is obvious in arteriotomy and 

 in wounds ; for the blood spurting from the arteries 

 escapes with force, now farther, now not so far, alter- 

 nately, or in jets ; and the jet always takes place with 

 the diastole of the artery, never with the systole. By 

 which it clearly appears that the artery is dilated by the 

 impulse of the blood ; for of itself it would not throw 

 the blood to such a distance, and whilst it was dilating ; 

 it ought rather to draw air into its cavity through the 

 wound, were those things true that are commonly stated 

 concerning the uses of the arteries. Nor let the thick- 

 ness of the arterial tunics impose upon us, and lead us 

 to conclude that the pulsative property proceeds along 

 them from the heart. For in several animals the arteries 

 do not apparently differ from the veins; and in extreme 

 parts of the body, where the arteries are minutely sub- 



