84 Motion of the Heart and Blood 



a way as to compress it, and prevent any blood from 

 passing upwards from the hand ; then, with a finger of 

 the other hand, streak the blood in the vein upwards 

 till it has passed the next valve above, (N, fig. 4,) the 

 vessel now remains empty ; but the finger at L being 

 removed for an instant, the vein is immediately filled 

 from below ; apply the finger again, and having in the 

 same manner streaked the blood upwards, again remove 

 the finger below, and again the vessel becomes dis- 

 tended as before ; and this repeat, say a thousand times, 

 in a short space of time. And now compute the quantity 

 of blood which you have thus pressed up beyond the 

 valve, and then multiplying the assumed quantity by 

 one thousand, you will find that so much blood has 

 passed through a certain portion of the vessel ; and 

 I do now believe that you will find yourself convinced 

 of the circulation of the blood, and of its rapid motion. 

 But if in this experiment you say that a violence is done 

 to nature, I do not doubt but that, if you proceed in 

 the same way, only taking as great a length of vein as 

 possible, and merely remark with what rapidity the 

 blood flows upwards, and fills the vessel from below, 

 you will come to the same conclusion. 



