HARVEY 



9 



Finally, take the famous passage in the eighth 

 chapter, De copid sanguinis transeuntis per cor e 

 vents in arterias, et de circulari motu sanguinis : — 



" And now, as for the great quantity and 

 forward movement of this blood on its way, when 

 I shall have said what things remain to be said 

 — though they are well worth considering, yet 

 they are so new and strange that I not only fear 

 harm from the envy of certain men, but am afraid 

 lest I make all men my enemies ; so does custom, 

 or a doctrine once imbibed and fixed down by 

 deep roots, like second nature, hold good among 

 all men, and reverence for antiquity constrains 

 them. Be that as it may, the die is cast now : 

 my hope is in the love of truth, and the candour 

 of learned minds. I bethought me how great 

 was the quantity of this blood. Both from the 

 dissection of living animals for the sake of experi- 

 ment, with opening of the arteries, with observa- 

 tions manifold ; and from the symmetry of the size 

 of the ventricles, and of the vessels entering and 

 leaving the heart — because Nature, doing nothing 

 in vain, cannot in vain have given such size to 

 these vessels above the rest — and from the harmoni- 

 ous and happy device of the valves and fibres, and 

 all other fabric of the heart ; and from many other 

 things — when I had again and again carefully 

 considered it all, and had turned it over in my 

 mind many times — I mean the great quantity of 

 the blood passing through, and the swiftness of its 

 passage — and I did not see how the juices of the 

 food in the stomach could help the veins from 

 being emptied and drained dry, and the arteries 

 contrariwise from being ruptured by the excessive 

 flow of blood into them, unless blood were always 



