THE CIRCULATION OF THE BLOOD. 443 



ligatures, of bleeding, and of other circumstances, 

 ought to manifest themselves in order to confirm 

 his view. That he referred to a multiplied and 

 varied experience for the evidence that it was so 

 confirmed, we have already said. Like all the best 

 philosophers of his time, he insists rigidly upon the 

 necessity of such experience. "In every science," 

 he says 18 , "be it what it will, a diligent observation 

 is requisite, and sense itself must be frequently 

 consulted. We must not rely upon other men's 

 experience, but our own, without which no man is 

 a proper disciple of any part of natural knowledge." 

 And by publishing his experiments, he trusts, he 

 adds, that he has enabled his reader "to be an 

 equitable umpire between Aristotle and Galen ;" or 

 rather, he might have said, to see how, in the pro- 

 motion of science, sense and reason, observation and 

 invention, have a mutual need of each other. 



We may observe further, that though Harvey's 

 glory, in the case now before us, rested upon his 

 having proved the reality of certain mechanical 

 movements and actions in the blood, this discovery, 

 and all other physiological truths, necessarily in- 

 volved the assumption of some peculiar agency 

 belonging to living things, different both from me- 

 chanical agency, and from chemical; and in short, 

 something vital, and not physical merely. For when 

 it was seen that the pulsation of the heart, its 



18 Generation of Animals, Pref. 



