LETTERS. 599 



on the matter. I could wish, also, that you had taken into 

 account not only what I have there denied, but likewise what I 

 have asserted on the transference of the blood from the arteries 

 into the veins ; especially as I there seem to have pointed out 

 some cause both for my inquiry and for my negation, to hint at 

 a certain cause. I confess, I say, nay, I even pointedly assert, 

 that I have never found any visible anastomoses. But this was 

 particularly said against Riolanus, who limited the circulation 

 of the blood to the larger vessels only, with which, there- 

 fore, these anastomoses, if any such there were, must have been 

 made conformable, viz. of ample size, and distinctly visible. 

 Although it be true, therefore, that I totally deny all anas- 

 tomoses of this description anastomoses in the way the word 

 is commonly understood, and as the meaning has come down 

 to us from Galen, viz. a direct conjunction between the ori- 

 fices of the [visible] arteries and veins I still admit, in the 

 same disquisition, that I have found what is equivalent to this 

 in three places, namely, in the plexus of the brain, in the 

 spermatic or preparing arteries and veins, and in the umbilical 

 arteries and veins. I shall now, therefore, for your sake, my 

 learned friend, enter somewhat more at large into my reasons 

 for rejecting the vulgar notion of the anastomoses, and explain 

 my own conjectures concerning the mode of transition of the 

 blood from the minute arteries into the finest veins. 



All reasonable medical men, both of ancient and modern 

 times, have believed in a mutual tranfusion, or accession and 

 recession of the blood between the arteries and the veins; and 

 for the sake of permitting this, they have imagined certain in- 

 conspicuous openings, or obscure foramina, through which the 

 blood flowed hither and thither, moving out of one vessel and 

 returning to it again. "Wherefore it is not wonderful that 

 Riolanus should in various places find that in the ancients 

 which is in harmony with the doctrine of a circulation. For a 

 circulation in such sort teaches nothing more than that the 

 blood floAvs incessantly from the veins into the arteries, and 

 from the arteries back again into the veins. But as the ancients 

 thought that this movement took place indeterminately, by a 

 kind of accident, in one and the same place, and through the 

 same channels, I imagine that they therefore found themselves 

 compelled to adopt a system of anastomoses, or fine mouths 



