n] Circulation of the Blood. 47 



" cava and right auricle of the heart, and this in such a quantity 

 " or in such a flux and reflux thither by the arteries, hither by 

 " the veins, as cannot possibly be supplied by the ingesta, and 

 " is much greater than can be required for mere purposes of 

 " nutrition ; it is absolutely necessary to conclude that the 

 " blood in the animal's body is impelled in a circle, and is in a 

 "state of ceaseless motion; that this is the act or function 

 " which the heart performs by means of its pulse ; and that it 

 " is the sole and only end of the motion and contraction of the 

 " heart." 



Harvey's argument is essentially a physical mechanical 

 argument ; the problem which he puts before himself to solve 

 is essentially a mechanical physical problem ; the solution of that 

 problem at which he arrived is essentially a mechanical solution 

 of the phenomena of the circulation. As we have seen, in the 

 minds of those before him the mechanical problems of the 

 circulation were mixed up with questions about the distribution 

 of the various kinds of spirits, the natural, vital and animal 

 spirits. With these questions Harvey does not deal at all. In 

 an early passage he says, " Whether or not the heart, besides 

 " propelling the blood giving it motion locally and distributing 

 " it to the body, adds anything else to it — heat, spirit, per- 

 " fection, — must be inquired into by and by, and decided upon 

 " other grounds." And never again, throughout the whole of 

 his argument, does he refer to the questions of the spirits. 



Yet his demonstration was the death-blow to the doctrine 

 of the l spirits.' The names it is true survived for long after- 

 wards, but the names were henceforward devoid of any really 

 essential meaning. For the view of the natural and vital 

 spirits was based on the supposed double supply of blood to all 

 the tissues of the body, the supply by the veins carrying natural 

 spirits and the supply by the arterial carrying vital spirits. 

 The essential feature of Harvey's new view was that the blood 

 through the body was the same blood, coursing again and again 

 through the body, passing from arteries to veins in the tissues, 

 and from veins to arteries through the lungs, heart, suffering 

 changes in the substance and pores of the tissues, changes 

 in the substance and pores of the lungs. 



