46 Harvey and the [lect. 



which succeeding anatomists have not added anything to our 

 knowledge." 



Fabricius, as we have seen, had used the now well-worn 

 experiment of pressing on the cutaneous veins of the bared 

 arm to demonstrate the existence of the valves ; but he 

 had used it to demonstrate their existence only. Blinded 

 by the conceptions of his time he could not see that the 

 same experiment gave the lie to his explanation of the pur- 

 pose of the valves, and demonstrated not only their existence, 

 but also their real use. Harvey, with the light of his new idea, 

 at once grasped the true meaning of the knotty bulgings. 



These however were not the only phenomena which now for 

 the first time received a reasonable explanation. Harvey was able 

 to point to many other things, to various details of the structure 

 and working of the heart, to various phenomena of the body 

 at large both in health and in disease as intelligible on his 

 new view, but incomprehensible on any other. 



If we trust, as indeed we must do, Harvey's own account of 

 the growth of this new idea in his own mind, we find that he 

 was not led to it in a straight and direct way by Fabricius' 

 discovery of the valves. It was not that the true action of 

 these led to the true view of the motion of the blood, but that 

 the true view of the motion of the blood led to the true 

 understanding of their use. To that true view of the motion 

 of blood he was led by a series of steps, each in turn based on 

 observations made on the heart as seen in the living animal, or 

 as he himself says ' repeated vivisections,' the great step of all 

 being that one by which he satisfied himself that the quantity 

 of blood driven out from the heart could not be supplied in any 

 other way than by a return of the blood from the arterial 

 endings in the body through the veins. As he himself says : 

 " Since all things, both argument and ocular demonstration, 

 "shew that the blood passes through the lungs and heart by 

 M the action of the ventricles, and is sent for distribution to all 

 " parts of the body, where it makes its way into the veins and 

 " pores of the flesh, and flows by the veins from the circum- 

 " ference on every side to the centre, from the lesser to the 

 " greater veins, and is by them finally discharged into the vena 



