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minuteli particles in the fibres of filhe.s,.\\heii at roll in tlieir natural 

 Hate, are, as it were, contracled in various annular folds or wrinkles ; 

 but when put in motion or extended for any purpofe, then all thofe 

 wrinkles and annidar foldings are opened or linoothed, and the 

 fibre becomes longer. 



The fame kind of annular wTinkles I alfo difcovcred in tlie optic 

 nenes of the fly now under conlidcration ; whence we may conclude, 

 that every one of thefe optic nerves is endued w ith the power of' 

 alternate extenfion and contraction equally -with the optic nerves in 

 a human eye. For it mull needs be, that when we move our eyes 

 from one fide to the other, their optic nerves will be more extended 

 than when we look flraight forwards. 



Having made this obfenation, I afked the limner whether he 

 could follow with his eye thofo circular marks or lines in the optic 

 nerves, and, upon his anfwering, that he could very plainly fee them, 

 I defired him to imitate them as nearly as he was able in his draw- 

 ings, and this is to be feen in^^, 2, and 3. 



Now if this fly had been dead fometime before I had differed 

 the eye, and taken out the optic nerves, I am very fure, that in 

 that cafe, I Ihould not haA^e difcerned any of thofe wrinkles 

 or contractions. In like manner we daily obferve in fiflies, that after 

 they have been dead fometime, their flefhy parts, if cut afunder, 

 do not become fhorter, which our people call krimpen*, and con- 

 fequently thofe parts of the fifli are neither fo firm, nor fo grateful 

 to the palate, as when they are cut afunder while the fifli is alive. 



Upon difcovery of fo many wonders, and of fuch perfedion in 

 the eye of a fly, we are again compelled to cry out ; How little do 

 we know ? And if this is feen in the eye of fo large a fly, it mull 



* Krimpen in Dutch lignifies to contraifl or gather up in folds, whence the phrafe to crimp 

 fifti is pliiiiily ilcrlvod; whidi cruel praftice fecms alfo to have been imported from Holland. 

 And it must be confcfled, that with all Mr. Lceuwenhock's abilities as a philofopher, he seems 

 not to have had much fenHbility of compaffion for the creatures which he fubjefted to his 

 examination. 



