122 WILLIAM HARVEY 



CHAPTER XII 



THAT THERE is A CIRCULATION OF THE BLOOD is SHOWN 

 FROM THE SECOND POSITION DEMONSTRATED 



IF these things be so, another point which I have already 

 referred to, viz., the continual passage of the blood through 

 the heart will also be confirmed. We have seen, that the 

 blood passes from the arteries into the veins, not from the 

 veins into the arteries; we have seen, farther, that almost 

 the whole of the blood may be withdrawn from a puncture 

 made in one of the cutaneous veins of the arm if a bandage 

 properly applied be used; we have seen, still farther, that 

 the blood flows so freely and rapidly that not only is the 

 whole quantity which was contained in the arm beyond the 

 ligature, and before the puncture was made, discharged, but 

 the whole which is contained in the body, both that of the 

 arteries and that of the veins. 



Whence we must admit, first, that the blood is sent along 

 with an impulse, and that it is urged with force below the 

 ligature; for it escapes with force, which force it receives 

 from the pulse and power of the heart; for the force and 

 motion of the blood are derived from the heart alone. Sec- 

 ond, that the afflux proceeds from the heart, and through 

 the heart by a course from the great veins; for it gets into 

 the parts below the ligature through the arteries, not 

 through the veins; and the arteries 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 impetuousity, 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 anyone, 

 for instance, 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 great- 

 est part of the blood being abstracted, faintings and 





