Chapter XII 



That There is a Circulation of the Blood 



Follows from the Proof of the Second 



Proposition 



SINCE these things are so, it establishes the 

 proof of what I said previously, that blood 

 continually passes through the heart. For we have 

 seen that blood spreads from the arteries to the 

 veins, not from veins to arteries; we have seen 

 further that almost the total amount of blood can 

 be taken from an arm if a single cutaneous vein 

 be opened with a lancet and a bandage properly 

 applied, and we have seen still further, that there 

 is so much force behind it, and so sufficient a flow 

 that the blood may easily and quickly be with- 

 drawn not only in the amount present in the arm 

 below the ligature before the cut was made, but 

 m the whole arm, and in the entire body, arteries 

 as well as veins. 



So it must be admitted, first, that blood is supplied 

 with force and impetus to push it beneath the liga- 

 ture, for it escapes with vigor, which is derived 

 from the pumping action of the heart and from this 

 alone. Likewise, it must be further admitted that 

 this flow comes from the heart, and by way of the 



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