HEART AND BLOOD. 51 



of the blood in the body, as well that of the veins as of the arte- 

 ries, drained away in the course of no long time some half hour 

 or less. Butchers are well aware of the fact and can bear witness 

 to it; for, cutting the throat of an ox and so dividing the vessels of 

 the neck, in less than a quarter of an hour they have all the ves- 

 sels bloodless the whole mass of blood has escaped. The same 

 thing also occasionally occurs with great rapidity in performing 

 amputations and removing tumours in the human subject. 



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

 say that in killing animals in the shambles, and performing am- 

 putations, the blood escaped in equal, if not perchance in larger 

 quantity by the veins than by the arteries. 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 impediment 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, wherefore in our dissections 

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

 in the arteries ; wherefore there is much in the right ventricle, 

 little in the left; circumstances which probably led the ancients 

 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 this perhaps : 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 em- 

 bryo, by the want of movement in the lungs and the alternate 



