112 WILLIAM HARVEY 



Nor would this argument lose of its force, did any one 

 say that in killing animals in the shambles, and perform- 

 ing amputations, the blood escaped in equal, if not per- 

 chance in larger quantity by the veins than by the ar- 

 teries. The contrary of this statement, indeed, is certainly 

 the truth; the veins, in fact, collapsing, and being without 

 any propelling power, and further, because of the impedi- 

 ment of the valves, as I shall show immediately, pour 

 out but very little blood; whilst the arteries spout it forth 

 with force abundantly, impetuously, and as if it were 

 propelled by a syringe. And then the experiment is easily 

 tried of leaving the vein untouched and only dividing the 

 artery in the neck of a sheep or dog, when it will be seen 

 with what force, in what abundance, and how quickly, 

 the whole blood in the body, of the veins as well as of 

 the arteries, is emptied. But the arteries receive blood 

 from the veins in no other way than by transmission 

 through the heart, as we have already seen; so that if the 

 aorta be tied at the base of the heart, and the carotid or 

 any other artery be opened, no one will now be surprised 

 to find it empty, and the veins only replete with blood. 



And now the cause is manifest, why in our dissections 

 we usually find so large a quantity of blood in the veins, 

 so little in the arteries; why there is much in the right 

 ventricle, little in the left, which probably led the an- 

 cients to believe that the arteries (as their name implies) 

 contained nothing but spirits during the life of an animal. 

 The true cause of the difference is perhaps this, that as 

 there is no passage to the arteries, save through the 

 lungs and heart, when an animal has ceased to breathe 

 and the lungs to move, the blood in the pulmonary artery 

 is prevented from passing into the pulmonary veins, and 

 from thence into the left ventricle of the heart; just as 

 we have already seen the same transit prevented in the 

 embryo, by the want of movement in the lungs and the 

 alternate opening and shutting of their hidden and in- 

 visible porosities and apertures. But the heart not ceas- 

 ing to act at the same precise moment as the lungs, but 

 surviving them and continuing to pulsate for a time, the 

 left ventricle and arteries go on distributing their blood 





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