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Ikin. But they have a third fide on the back of each of them, and 

 their figure, in that refped, i& hke that of a fmall f\vord,which, by 

 reafon of its fmallnefs, muft neceflarily have a third fide to give it 

 Itrength, agreeing, in that refpcdl, with thefe llings of the Gnat. 



Hitherto it has appeared no otherwife to me tlian that each of 

 thefe barbed llings has the barbs or hooks only on one fide, and 

 M'hen they He on the infide of their cafe, or more properly, within 

 the thickeft of the flings, their flat fides are clofe together, and 

 thofe fides which are barbed lie on the outfide, fo that when all the 

 pieces of the fling are placed together in order, they exhibit, when 

 taken out of the flieath, the appearance of a fingle fling barbed or 

 hooked on each fide. 



Fig. 10, V^WX, reprefents one of the two barbed flings taken 

 out of the cavity of the other piece, one of them being a little 

 longer than the other. 



Fig. 11, a b c, reprefents a part of one of the two laft mentioned 

 flings, which, by reafon of its exceeding thinnefs, was bent in this 

 fliape, but in this pofition, the hooks or barbs cannot be diflin- 

 guifhed ; placing the flat fide of this before the micro fcope, the 

 point of it appeared as Sitjig. 12. Upon turning it round a httle, 

 the point appeared as a^t Jig. 13, and turning it flill more, the hooks 

 became vifible, as is Ihewn at^g". 14. 



If we confider the formation of thefe flings, though we know not 

 how the Gnat flrikes them into our bodies, or moves them about 

 when there, we may, never thelefs, eafily conceive, that when 

 driven within the Ikin, they may make a very fenfible, though mi- - 

 nute wound, and by reafon of their length, a much deeper one 

 than is occafioned by lice, fleas, or other fmall vermin. Again, fo 

 long as the Gnat is fucking the blood which iflues out of the 

 wounded veflels, there will not any fwelling appear. But when 

 it draws out the flings, the juices of the wounded veflels continuing 

 to ilTue, there muft neceflarily arife a greater fwelling than ufual, 

 becaufe, as I before faid, the flings enter fo deep, and another rea- 



