HARVEY AND EXPERIMENTAL OBSERVATION 5 1 



of cither observations or experiments by him). He also laid 

 hold of a still more important conception, viz., that some of 

 the blood passes from the left side of the heart through the 

 arteries of the body, and returns to the right side of the heart 

 by the veins. But a fair consideration of the claims of these 

 men as forerunners of Harvey requires quotations from their 

 works and a critical examination of the evidence thus adduced . 

 This has been excellently done by Michael Foster in his Lec- 

 tures on the History oj Physiology. Further considerations 

 of this aspect of the question would lie beyond the purposes 

 of this book. 



At most, before Harvey, the circuit through the lungs had 

 been vaguely divined by Galen, Servetus, Columbus, and 

 Caesalpinus, and the latter had supposed some blood to pass 

 from the heart by the arteries and to return to it by the veins; 

 but no one had arrived at an idea of a complete circulation 

 of all the blood through the system, and no one had grasped 

 the consequences involved in such a conception. Harvey's 

 idea of the movement of the heart (De Motu Cordis) was new; 

 his notion of the circulation (et Sanguinis) was new; and 

 his method of demonstrating these was new. 



Harvey's Argument. — The gist of Harvey's arguments is 

 indicated in the following propositions quoted with slight 

 modifications from Hall's Physiology: (I) The heart pas- 

 sively dilates and actively contracts; (II) the auricles contract 

 before the ventricles do; (III) the contraction of the auricles 

 forces the blood into the ventricles; (IV) the arteries have 

 no "pulsific power," i.e., they dilate passively, since the pul- 

 sation of the arteries is nothing else than the impulse of the 

 blood \vithin them; (V) the heart is the organ of propulsion 

 of the blood; (VI) in passing from the right ventricle to the 

 left auricle the blood transudes through the parenchyma of 

 the lungs; (VII) the quantity and rate of passage of the blood 

 peripherally from the heart makes it a physical necessity that 



