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it has firft pafled into the heart ; but fince, in one of the obferva- 

 tions I was making only for my amufement I faw the contrary, I 

 have caufed a drawing to be made of that appearance, in which 

 drawing I direAed the blood-veflels to be reprelentcd rather larger 

 than they appeared to me, and in the middle of the fmall veirds there 

 are no dots : thofe dots, in other parts of the figure, denote the 

 globules of blood, in order more plainly to defcribe the circulation. 



Let us fuppofe A B, in.,fig- 32, to be a vein in which, by the mi- 

 crofcope, the blood may be feen di-iven with great fwiftnefs from 

 B to A. From this blood-veiiel iflued two fmall branches, repre- 

 fented at the letters C and D, which were united between the let- 

 ters E and F. 



On the other hand, the letters II I exhibit an artery through which 

 the blood was, with like fwiftnefs, driven from H to I, and from 

 this artery, H I, proceeded a branch, fliewn at the letters K F L. 



Now the blood running from K towards F is united to the velTel 

 F at that letter, and by this means the blood illuing out of the 

 artery is in part infufed into a vein and carried from F to G ; and 

 the fame quantity of blood (as according to my moll accurate 

 obfervations appeared) as was carried from K F to G downwards, fo 

 much blood of that, which was carried from C E to F, was carried 

 upwards from F to L ; fo that as much of the arterial blood as the 

 velfcl, KF, conveyed into the veflel, FG, fo much of the venal 

 blood did the velfel, C E, convey into the veflel, F L. And, though 

 I have often enjoyed great pleafure in viewing the circulation of the 

 blood, this fpeclacle, which I have been juft defcribing, was more 

 delightful than any other, becaufe I could moft clearly and ditlindly 

 fee the objeds I have defcribed, and alfo, becaufe I never before faw 

 fuch a conjundion or communication between the blood- veflels. 



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Vol. XL H h 



