HEART AND BLOOD. 61 



ture through the arteries, not through the veins ; and the ar- 

 teries nowhere receive blood from the veins, nowhere receive 

 blood save and except from the left ventricle of the heart. 

 Nor could so large a quantity of blood be drawn from one vein 

 (a ligature having been duly applied), nor with such impetuosity, 

 such readiness, such celerity, unless through the medium of the 

 impelling power of the heart. 



But if all things be as they are now represented, we shall 

 feel ourselves at liberty to calculate the quantity of the blood, 

 and to reason on its circular motion. Should any one, for in- 

 stance, in performing phlebotomy, suffer the blood to flow in 

 the manner it usually does, with force and freely, for some half 

 hour or so, no question but that the greatest part of the blood 

 being abstracted, faintings and syncopes would ensue, and that 

 not only would the arteries but the great veins also be nearly 

 emptied of their contents. It is only consonant with reason 

 to conclude that in the course of the half hour hinted at, so 

 much as has escaped has also passed from the great veins 

 through the heart into the aorta. And further, if we calculate 

 how many ounces flow through one arm, or how many pass in 

 twenty or thirty pulsations under the medium ligature, we shall 

 have some grounds for estimating how much passes through the 

 other arm in the same space of time ; how much through both 

 lower extremities, how much through the neck on either side, 

 and through all the other arteries and veins of the body, all of 

 which have been supplied with fresh blood, and as this blood 

 must have passed through the lungs and ventricles of the heart, 

 and must have come from the great veins, we shall perceive 

 that a circulation is absolutely necessary, seeing that the quan- 

 tities hinted at cannot be supplied immediately from the ingesta, 

 and are vastly more than can be requisite for the mere nutrition 

 of the parts. 



It is still further to be observed, that the truths contended 

 for are sometimes confirmed in another way; for having tied 

 up the arm properly, and made the puncture duly, still, if from 

 alarm or any other causes, a state of faintness supervenes, in 

 which the heart always pulsates more languidly, the blood does 

 not flow freely, but distils by drops only. The reason is, that 

 with the somewhat greater than usual resistance offered to the 

 transit of the blood by the bandage, coupled with the weaker 



