NOTES ON LETTER 389. LETTER 75 Q47 
which T'richomonas is supposed to have been described, it is 
clear that Wenyon must here refer to one or other of the 
“animalcules’’ which we have just discussed—but which 
one, I cannot even guess. To me it is obvious that they were 
all bacteria: but Wenyon takes the view that none of them 
could have been, since he considers that bacteria ‘“‘ were quite 
beyond the scope of the simple magnifying apparatus used by 
Leeuwenhoek.” ? 
Thus, while Singer finds, in Leeuwenhoek’s words and 
pictures, more bacteria than Leeuwenhoek himself, Wenyon is 
able to recognize none at all! 
Some further researches on the ‘“animalcules” in the 
human mouth were reported by Leeuwenhoek nine years 
later. His letter runs as follows: ? 
In my letter of the 12th* of September, 1683, I spake, 
among other things, of the living creatures that are in 
the white matter which lieth, or groweth, betwixt or 
upon one’s front teeth or one’s grinders. Since that 
time, and especially in the last two or three years, I have 
examined this stuff divers times; but to my surprise, I 
could discern no living creatures in it. 
1 Wenyon (1926), p. 3. 
2 From Letter 75. 16 September 1692. To the Royal Society. 
MS.Roy.Soc. Printed in full in Brieven, Vol. II, p. 508: Opera Omnia, 
Vol. II, p. 307 (1st pagination). The Dutch version first appeared in 1693 
(Derde Vervolg d. Brieven), the Latin in 1695 (Arc. Nat. Det., p. 334). No 
English translation was ever published in the Phil. Trans., and so far as I 
am aware no English version has yet appeared in print. (Hoole did not 
translate the relevant passages in this letter.) A German paraphrase—of a 
fragment only—is given by Léftler (1887, p. 6), who misdates the epistle 
October 1.—The printed Dutch version follows the original MS. so closely 
that few annotations are necessary : while the Latin version in Opera Omnia 
(ed. noviss., 1722)—by an unknown hand—is one of the best translations I 
have ever read. Barring a few trivial misprints, it renders its Dutch 
prototype with wonderful faithfulness.—The originals of the illustrations 
are lost ; the MS. in the Roy.Soc. collection being accompanied by a proof 
of the engraved plate sent by L. himself in place of the original sketches. 
* As noted already (p. 237, note 2), the correct date of this letter— 
as written by L. himself on the MS.—is not the 12th but the 17th of 
September. 
