THE CIRCULATION OF THE BLOOD 453 



THE MAN WHO DISCOVEKED THE CIECULATION OF 



THE BLOOD 



By Professor D. FRASER HARRIS, M.D., CM., D.Sc, F.R.S.E. 



DALHOUSIE UNIVERSITY 



f I THE discoverer of the circulation of the blood was a London doctor 

 -*- called William Harvey. 



The discovery of the circulation of the blood is the foundation of 

 modern medicine; it was epoch-making, for it made possible that mar- 

 velous epoch in which we have seen the laws of living matter discovered 

 and the actual, physical causes of the most mysterious diseases revealed. 

 Harvey closed the dark ages of the science of the living ; physiologically 

 he "allured to brighter worlds, and led the way." Until it could be 

 known that the blood, the same blood, moved round and round the body 

 under the force of the propulsion of the heart, and that it traversed 

 heart and lungs and all body-vessels in its closed circuit, there could be 

 no physiology, no pathology, no therapeutics, no rational medicine: no 

 such procedure as transfusion of blood. To understand what it was 

 that Harvey discovered, we need to know what was believed as regards 

 the movement of the blood before his time. 



The oldest idea of all was that only the veins contain blood, the 

 arteries air. Galen had corrected this latter mistake by tying a cord 

 above and one below a length of artery and cutting out the piece above 

 and below the ligatures; blood, of course, and not air was found inside. 

 It was thought that blood went up and down the veins like the ebb and 

 flow of a tide, that "crude" blood was made in the liver and taken to 

 the heart to be purified. The heat supposed to be produced in this 

 process was believed to make it necessary to cool the heart by drawing 

 in air in the act of breathing, and this was regarded as the function of 

 respiration even as late as the time of Haller, that is, the middle of the 

 eighteenth century. The pulse or opening up of the arteries was re- 

 garded as an active thing on their part, blood not being forced into 

 them by the heart but drawn into them by their own suction like a 

 bellows draws in air. But Harvey said the heart is the pump, and the 

 arteries are filled by its forcing its blood into them. 



Harvey advanced not one or two but more like a dozen proofs of the 

 circulation. His contention is — the blood in the arteries moves towards 

 the tissues, thence towards the veins, it is collected in the right auricle 

 of the heart, whence it flows to the right ventricle, this on contracting 

 drives it through the lungs, whence it flows to the left auricle, passes to 

 left ventricle and so is ready to be sent to the body again. Galen had 



