72 INTRODUCTION 



is prevented from being lost, and the wound is closed. " 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 wall over the tube, 3'ou will no longer 

 see the artery beating beyond the ligature." I have never per- 

 formed 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 

 that 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 property 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 as if they are filled like skins, But the con- 

 trary is obvious in arteriotomy and in wounds; for the blood 

 spurting from the arteries escapes with force, now farther, now 

 not so far, alternately, 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 with 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. Do 

 not let the thickness 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 subdivided, as in the brain, 

 the hand, etc., no one could distinguish the arteries from the 

 veins by the dissimilar characters of their coats: the tunics of 

 both are identical. And then, in the aneurism proceeding from 

 a wounded or eroded artery, the pulsation is precisely the same as 

 in the other arteries, and yet it has no proper arterial covering. 

 To this the learned Riolanus testifies along with me, in his 

 Seventh Book. 



Nor let any one imagine that the uses of the pulse and the 

 respiration are the same, because, under the influences of the 

 same causes, such as running, anger, the warm bath, or any 





