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I have often, with great pleafure, obferved the texture of the 

 Nerves, which are compoied of very minute veflels of an incredible 

 thinnefs, and which, running along by the lides of each other, con- 

 ftitute a Nerve ; the cavity of each of thefe fmall veflels is about two 

 thirds its diameter; and in order to examine them I direded the 

 fpinal marrow of three cows and one flieep to be brought to my 

 houfe, that I might extra6l from thence the Nerves. 



I confider it as a misfortune, that I have not been able to exhibit 

 the cavities in thefe Nerves to others, but no fooner do I bring them 

 before my sight, than in a very Ihort time, even lefs than the fpace 

 of a minute, they fo contract by evaporation, that the wonderful 

 obje^L vaniflies and cannot be reflored. And I not only faw the 

 fize or circumference of thefe veflels, (fome hundreds of which go 

 to the compoiition of a nerve no larger than a hair of a man's 

 beard), but fome of their cavities I could as plainly diftinguifh, as if 

 we were to pierce many holes in a paper w ith a fmall needle, and 

 hold them up again IT- the fun. And although thefe cavities, or the 

 orifices of thefe veflels are fo wonderfully minute, I have feen liv- 

 ing creatures in the waters, which could have moved and fwam 

 about in them with freedom. In fliort, the minutenefs of fome 

 things on this earth is fuch as feems to exceed all belief. 



I cut fome of thefe nerves into fmall flices, or round pieces, each 

 little or nothing larger than the hair of a man's beard, and wetting 

 them, I placed them on a glafs to dry ; when dried and viewed by 

 the microfcope, I faw in them many fmall knobs or rifings, which 

 I concluded to arife from hence, that the many fmall veflels of 

 which a Angle nerve is compofed, became contradled upon the 

 evaporation of the moillure they contain, and thence arofe in protu- 

 berances. 



It often happened to me, that w^hen I moifl:ened one of thefe 

 fmall flices of a nerve after it had been dried, and looked at it 

 through the microfcope, that I faw fome fmall particles in great 

 numbers, fwiiuming about in the water : thefe particles I judged. 



