738 PHILOSOPHICAL TRANSACTIONS. [aNNO I672. 



ductus was, that we very distinctly saw the figure and the whole structure of it 

 when the composition wherewith it had been filled was refrigerated and hard- 

 ened. For we found, that that ductus did ascend unto the right side of the 

 heart, keeping one and the same size, which was no more than -V of an inch ; 

 that afterwards it was enlarged to ^ of an inch in diameter; that in this en- 

 largement its tunicle on the ri^ht side of the vertebrce was, as it were, pierced 

 by four small holes, distant -jV of an inch from one another, and all disposed 

 in a row ; into which holes the said composition had not been able to penetrate ; 

 that the same ductus, after having retaken its first size, had two appendixes 

 fashioned like sacks; that there was yet a third appendix beneath the dilatation; 

 that the first and highest appendix was of the form and bigness of a small pha- 

 seolus ; that the third, which was beneath the dilatation, was like to the second ; 

 that they had all a straight orifice ; and that the last was full of chyle conspissate, 

 so that the composition could not enter there, as it had done into the other. 



A second Letter of P. Pardies, ivritten to the Editor from Paris, 

 May 21, 1672, to Mr. Newton's Answer made to his first Letter, 

 printed in N° 84. N" 85, p. 5012. Translated from the Latin, 



I have received your letter, with the observations of the very ingenious Mr. 

 Newton, in which he answers my difficulties, which I have read with great 

 pleasure. And first, with respect to that experiment of the greater breadth of 

 the colours than what is required by the common theory of refractions ; I con- 

 fess that I supposed the refractions at the opposite sides of the prism unequal, 

 till informed by the letter in the Transactions, that the greater breadth was 

 observed by Newton in that case in which the refractions are supposed recipro- 

 cally equal, in the manner mentioned in those observations. But since I now see 

 that it was in that case that the greater breadth of the colours was observed, on 

 that head I find no further difficulty. I say on that head ; for the greater 

 leno-th of the image may be otherwise accounted for, than by the different 

 refrangibility of the rays. For according to that hypothesis, which is explained 

 at large by Grimaldi, and in which it is supposed that light is a certain substance 

 very rapidly moved, there may take place some diffusion of the rays of light 

 after their passage and decussation in the hole. Also on that other hypothesis, 

 in which light is made to proceed by certain undulations of a subtile matter, as 

 explained by Mr. Hook, colours maybe explained by a certain diffusion and ex- 

 pansion of the undulations, made on the sides of the rays beyond the hole by 



that there is no other channel by which the chyle is conveyed into the blood than that of the thoracic 

 duct, which generally opens into the left subclavian vein at the angle formed by it and tlie internal 

 jugular vein. Sometimes however it is inserted directly into the internal jugular.] 



