( 9^ ) 



fome final] veffels ; defiring him, at the fame time, to obfcrve, that 

 all tho'e veni?ls thrcugli which t!ie blcod was driven outwards to the 

 cxtrcinitios, v>erc named arteries, but where the blood, when arrived 

 at the fmallefl veilels, began to take its courfe back again, there 

 they were called veins, although it plainly appeared that the vcllels 

 \\ ere one and the fame. 



The limner could not fufTiciently admire this fpe6lacle of the blood 

 circulating in fuch minute velTels, arifing out of the larger ones ; and 

 he was equally in admiration at the blood's returning from thole 

 very fmall vefTels into the larger. And as the eel continued quiet 

 longer than ufual, without moving its tail, I frequently defired the 

 limner that he would, as long as pollible, keep his eye fixed on this 

 current of the blood, in order to imprint the idea on his memory. 

 At length, he put his hand to paper, and made a rough fketch of fome 

 blood-vellels and their ramifications, or branches ; and he repeated 

 liis obfervation and his drawing, until he had compleatly traced fix 

 fcvcral blood-velTels, namely, three arteries, and as many veins, witli 

 their ramifications, with all tlie accuracy he was able, faying, he had 

 now fufficient materials to make a perfeft drawing, fo as to dcfcribe 

 the cxa6l proportion both of the larger and fmaller vefiels. 



In Plate IV. ^^. 7, and in the fpace between i , 2, 3, 4, are reprc- 

 fented fix of tliefe blood-vefiels, which I directed to be drawn on 

 rather a larger fcalc than the firft fketch taken of them, in order that 

 the fcveral veficls might be eafier difiinguifhed ; therefore this figure 

 (liews them about twice as large as tliey appeared to the limner 

 through the microfcope. 



Thefe velTels were not at the very extremity of the fifii's tail, but 

 El little below it, towards the end of the fin. And that part, or fpot, 

 which the limner faw through the microfcope, and the feveral blood- 

 veflels of which he made the drawing, did not, in my judgment, take 

 up as much fpace as is occupied by a large grain of fand ; for though 

 the view of the microfcope might include the compafs of four fuch 



