On the circulation of the blood in the tail of an Eel, and in the tails 

 and fins of other fflies : ivith a particular defcription of the Au- 

 thor s apparatus for viewing it, 



x\MONG * other objeds, wherein I have viewed the circulation of 

 the blood, was an Eel, and in the fin of its tail, I faw the blood cir- 

 culating through an incredible number of arteries and veins of vari- 

 ous fizes; and although thofe blood-veflels were difperfed promif- 

 cuoully one among another, yet I could very plainly diftinguilli the 

 arteries and veins. 



Upon fixing my eye almoft at the extremity of the tail fin, I 

 there faw fuch a number of minute blood-veflels, that it was impofli- 

 ble forme to difcern the circulation in the minuteft of thofe veflels. 

 This fjn being a little dirty, I took a piece of linen cloth, and gently 

 wiped it twice, to get a better view ; but I found that in that flight 

 touch, many of the external blood vellels were fo injured, that many 

 particles of blood iflued forth, caufing the extreme parts of the fin 

 to appear red, and they were alfo a little diftorted : I alfo plainly 

 faw in all the arteries, however minute, a fi:rong and quick fuccel- 

 five elevation, with a protrufion of the blood ; and, upon attending 

 to a large artery in the tail, I there faw the protrufion of blood, de- 

 rived from the heart, to be much more vehement. 



I alfo placed before my fight one of the two fins which the Eel 

 has next its head, and there I faw the blood circulating in as many 

 diftindl places as I have jufl; mentioned refpefting the tail fin. And 

 when I endeavoured to purfue the circulation to the extremity of this 



• See more on this fubjeft, in Vol. I. p. 89. et m*?. 



