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fig. 5, is fliewn part of tlie body and the tail of the fame fifli, as fecn 

 through the microfcope. DE is a fin on the back, and L M, another 

 under the belly, near the tail, and FGHIK is the fin of the tail, 

 wherein are to be numbered feventeen fmall bones. 



Thefe fmall bones, contrived by Nature to give ftrength to the 

 fin, were formed with joints ; and I could fee that they were com- 

 pofed of oblong particles, which, probably, were hollow tubes ; the 

 pellicle, or membrane, which covered them, and compofed the 

 greateft part of the fin, was alfo formed of oblong parts, but thefe 

 things the limner could not perceive, becaufe the fifli being then 

 dead, they were become invifible. 



I have before faid, that on each fide of thefe boney parts of the 

 tail I had diflin6lly feen the compleat circulation of tlie blood, and 

 this was in thirty-four places, two between each bone ; that is, there 

 were in this fifh's tail fixty-eight blood vefl'els ; namely, thirty-four 

 arteries, and as many veins, befides tliofe vefi'els that, probably, 

 were in the fmalleft part of the fin, about F or K, wliich I did not 

 attend to. 



To Ihew this circulation more plainly, I caufed one of the boney 

 parts of the tail to be drawn fomewhat more magnified, which is re- 

 prefented a^.fig. 6, O PQ R, Clofe to each fide of this bone lies an 

 artery, which in the figure is pictured at S T and W X, and in thefe 

 veflels are reprefented the particles of blood, which appear of a round 

 figure. Here the blood was to be feen running with a fwift courfe 

 from S to T, and with the fame fwiftnefs returning back from T to 

 V, fo that ST is an artery, and T V a vein, and yet, both of them 

 but one blood-veffel, continued and prolonged. In like manner, were 

 the blood-veflels on the other fide of the bone at WX Y. But thefe 

 arteries and veins were not at fo great a proportionate diftance as 

 here reprefented, for, in many places, they were fo clofe as to touch 

 each other. 



