52 DESCARTES. 



reflux. Nor do we need to seek any other reason 

 for the number of these pellicles beyond this that 

 the orifice of the venous artery being of an oval 

 shape from the nature of its situation, can be 

 adequately closed with two, whereas the others 

 being round are more conveniently closed with 

 three. Besides, I wish such persons to observe that 

 the grand artery and the arterial vein are of much 

 harder and firmer texture than the venous artery 

 and the hollow vein ; and that the two last expand 

 before entering the heart, and there form, as it 

 were, two pouches denominated the auricles of the 

 heart, which are composed of a substance similar to 

 that of the heart itself; and that there is always 

 more warmth in the heart than in any other part of 

 the body; and, finally, that this heat is capable of 

 causing any drop of blood that passes into the 

 cavities rapidly to expand and dilate, just as all 

 liquors do when allowed to fall drop by drop into 

 a highly heated vessel. 



For, after these things, it is not necessary for me 

 to say anything more with a view to explain the 

 motion of the heart, except that when its cavities 

 are not full of blood, into these the blood of neces- 

 sity flows, from the hollow vein into the right, and 

 from the venous artery into the left ; because these 

 two vessels are always full of blood, and their 

 orifices, which are turned towards the heart, cannot 

 then be closed. But as soon as two drops of blood 

 have thus passed, one into each of the cavities, these 

 drops which cannot but be very large, because the 

 orifices through which they pass are wide, and the 



