DISCOURSE ON METHOD. 55 



from coming forward through the arteries, because 

 these are situated below the veins, and their cover- 

 ings, from their greater consistency, are more diffi- 

 cult to compress; and also that the blood which 

 comes from the heart tends to pass through them to 

 the hand with greater force than it does to return 

 from the hand to the heart through the veins. And 

 since the latter current escapes from the arm by the 

 opening made in one of the veins, there must of 

 necessity be certain passages below the ligature, 

 that is, towards the extremities of the arm, through 

 which it can come thither from the arteries. This 

 physician likewise abundantly establishes what he 

 has advanced respecting the motion of the blood, 

 from the existence of certain pellicles, so disposed 

 in various places along the course of the veins, in 

 the manner of small valves, as not to permit the 

 blood to pass from the middle of the body towards 

 the extremities, but only to return from the extrem- 

 ities to the heart; and farther, from experience 

 which shows that all the blood which is in the body 

 may flow out of it in a very short time through a 

 single artery that has been cut, even although this 

 had been closely tied in the immediate neighbour- 

 hood of the heart, and cut between the heart and the 

 ligature, so as to prevent the supposition that the 

 blood flowing out of it could come from any other 

 quarter than the heart. 



But there are many other circumstances which 

 evince that what I have alleged is the true cause of 

 the motion of the blood : thus, in the first place, the 

 difference that is observed between the blood which 



