( ii8 ) 



of thefe teeth by me four or five clays before I broke them open, 

 (in which time all the internal nioilhn-e was evaporated), I obferved 

 in fome places within the tooth, a bloody fubflance which had pene- 

 trated into the boney tubuli, giving fome of them a reddilh colour. 



It is my cuftom, every morning, to rub my teeth with fait, and 

 afterwards to walh my mouth, and after eating I always clean my 

 large teeth with a tooth-pick, and fometinies rub them very hard 

 with a cloth. By thefe means, my teeth are fo clean and white, 

 that few perfons of my age * can fliew fo good a fet, nor do my 

 gums ever bleed, although I rub them hard with fait ; and yet I 

 cannot keep my teeth fo clean, but that upon examining them 

 with a magnifying glafs, I have obferved a fort of white fubRance 

 colle6led between them, in confiftence like a mixture of flour 

 and water, hi reflecting on this fubflance, I thought it probable, 

 (though I could not obferve any motion in it,) that it might con- 

 tain fome living creatures. Having therefore mixed it with rain 

 water, whicli I knew was perfeffly pure, I found, to my great 

 furprile, that it contained many very fmall animalcules, the mo- 

 tions of which were very pleafing to behold. The largeit fort 

 of them is reprefented in Plate "V-fg. 3, at A, and thefe had the 

 greateft, and the quickeft motion, leaping about in the fluid, 

 like the fifti called a Jack ; the number of thefe was very fmall. 

 The fecond fort are reprefented at B, thefe often had a kind of 

 whirling motion, and fometimes moved in the dire61:ion repre- 

 fented by the dotted line C D, thefe were more in number. Of 

 the third fort, I could not well afcertain the figure, for fometimes 

 they feemed roundifti but oblong, and fometimes perfedlly round. 

 Thefe were fo fmall, that they did not appear larger than repre- 

 fented at E. The motion of thefe little creatures, one among 

 another, may be imagined like that of a great number of gnats, or 

 flies fporting in the air. From the appearance of thefe, to me, I 



* Mr. Leeuwenhoek, at the time of writing this, was upwards of fifty years of age. 



