LETTER 110. 10 SEPTEMBER 1697 253 
tooth ; which I succeeded in doing, for the tooth was 
left hanging to only a small bit of flesh, and I was able 
to snip it off very easily. 
The crown of this tooth was nearly all decayed, while 
its roots consisted of two branches ; so that the very roots 
were uncommon hollow,’ and the holes in them were 
stuffed with a soft matter. 
I took this stuff out of the hollows in the roots, and 
mixed it with clean rain-water, and set it before the 
magnifying-glass so as to see if there were as many living 
creatures in it as I had aforetime discovered in such 
material: and I must confess that the whole stuff seemed 
to me to be alive. But notwithstanding the number of 
these animalcules was so extraordinarily great (though 
they were so little withal, that ’twould take a thousand 
million of some of ’em to make up the bulk of a coarse 
sand-grain, and though several thousands were a-swim- 
ming in a quantity of water that was no bigger than a 
coarse sand-grain is), yet their number appeared even 
greater than it really was: because the animalcules, with 
their strong swimming through the water, put many little 
particles which had no life in them into a like motion, 
so that many people might well have taken these particles 
for living creatures too. 
These were Leeuwenhoek’s last recorded observations on 
the bacteria of the mouth, but there is another reference to 
bacteria which he saw in a decoction of the “fur” off his own 
tongue some years later. Although these were obviously 
putrefactive organisms, and not species proper to the human 
1 The original words are 200 dat selfs de Wortels boven gemeen hol waren. 
The Latin translator apparently took this to mean that the wpper parts of 
the roots were hollowed out (as is very probable, of course), for he renders 
these words “ superior wtriusque radicis pars admodum erat excavata”’: but 
boven gemeen is a common expression with L., and always means 
“unusually” or “out of the common run of experience.” In the Phil. 
Trans. the words “boven gemeen hol” are absurdly mistranslated 
“extraordinary whole ”’ 
2 de groote van een grof zand printed letter . . . geen grof zand MS. 
