442 HISTORY OF PHYSIOLOGY. 



Sect. 4. Bearing of the Discovery on the Progress 



of Physiology. 



IN considering the intellectual processes by which 

 Harvey's discoveries were made, it is impossible 

 not to notice, that the recognition of a creative pur- 

 pose, which, as we have said, appears in all sound 

 physiological reasonings, prevails eminently here. 

 " I remember," says Boyle, " that when I asked our 

 famous Harvey what were the things that induced 

 him to think of a circulation of the blood, he 

 answered me, that when he took notice that the 

 valves in the veins of so many parts of the body 

 were so placed, that they gave a free passage to the 

 blood towards the heart, but opposed the passage 

 of the venal blood the contrary way; he was incited 

 to imagine that so provident a cause as Nature had 

 not placed so many valves without design ; and no 

 design seemed more probable than that the blood 

 should be sent through the arteries, and return 

 through the veins, whose valves did not oppose its 

 course that way." 



We may notice further, that this discovery im- 

 plied the usual conditions, distinct general notions, 

 careful observation of many facts, and the mental 

 act of bringing together these elements of truth. 

 Harvey must have possessed clear views of the mo- 

 tions and pressures of a fluid circulating in ramify- 

 ing tubes, to enable him to see how the position of 

 valves, the pulsation of the heart, the effects of 



