Motion of the 



(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 instance, 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 ex- 

 tremities, 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 quantities 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 



