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equal diilindlnefs, the fmall veflels of every dcfcription, as I had 

 feen them in the Brain of a Turkey ; but alfo as clearly and dif- 

 tindly as I had done in the Brain of an Ox and a Sheep, and in all 

 other refpects, there was no difference to be noted than between 

 the magnitude of a Sparrow's Brain and that of an Ox ; fo that as 

 before obferved, there is no difference between them (except in the 

 large blood veflHs), fave that the fizc in the larger animal is owing 

 to its being compofed of a greater number of parts. And when, 

 with my utmoll attention, I examined the vitreous fubllance 

 (othcrwife called the corticle) of the Brain, it feems to me 

 wholly to confill of no other parts, than an incomprehenlible mul- 

 titude of the minuted veffels, which adjoin fo clofely to each other, 

 that by their tranfparency they reprefent a glafly fubftance, when 

 viewed by the microfcope, and which appeared more plainly to 

 me in the fmall Brain of the Sparrow, than in the large one of 

 the Ox. 



Now, though I am certain of the truth of my opinion, nor have 

 any fcruple or doubt refpecling the exigence of the minute veflels 

 I have been defcribing, I had rather it were doubted of by others, 

 if perhaps my fight has deceived me, but which I fee no reafon to 

 believe. For we fhall ceafe to doubt or wonder at the minutenefe 

 of thefe vcllels, if we recoiled; and duly confider the minutenefs 

 of thofe which the fmalleft animalcules we view mull be furnifhed 

 with ; or what will feem lefs wonderful, if we confider what I am 

 going to relate, refpeding the fmallelt veflels in our own bodies. 

 For being lately bufied in diflcding a human eye; in the black mem- 

 brane which covers the cavity of the eye, and by which the rays 

 of light are reflected, I faw ftreaks or veflels the fmallell that I 

 had ever difcovered ; and being defirous to judge of their flender- 

 nefs, I took a large grain of fand, the axis of which was almoft 

 the thirtieth part of an inch : viewing this grain of fand by the 

 microfcope, I judged that its axis might be divided at leaft into 

 330 equal parts ; and finding that eight of thofe fmall vcfleU', placed 



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