150 
LEEUWENHOEK AND HIS ‘“‘ LITTLE ANIMALS” 
that they were a bit flat in front, furnished with divers 
little legs, which during motion stuck out a bit beyond 
the body; and at the hind end of the body there was a 
round spot, running out headwards in a dark streak, 
looking very much like the guts or the blood in the 
body of a louse,’ as seen with the naked eye. 
The 19th of September, the numerous long and roundish 
little animalcules were much slower in their motion, and 
amany of them lay without any motion at all. The 
animalcules with tails were increased to yet greater 
numbers: the animalcules equally thick throughout, and 
those that had the figure of a pear, were in number as 
before. 
My further observations I have not recorded: I can 
only say this, that in the course of a day or two the 
water again got so thick, that all the animalcules that 
were still in it moved themselves very slow; and 2 or 
3 days after I had poured in well-water once more, I 
perceived the small animalcules in as vast a number as 
ever heretofore. 
[Observations on Vinegar. ] 
For the last 2 or 3 years I have not been able to find 
any little worms, or eels, in the vinegar that I keep in 
a cask in my cellar, for my household. I now®* drew 
off } pint of this vinegar into a glass, and set it in my 
closet, covering it over with a paper to keep off the dust : 
and after the lapse of 11 days, I did perceive therein 
little eels, which multiplied from day to day. I have 
divers times put a little vinegar into a little pepper-water, 
and have always seen that as soon as the pepper-water 
‘4 more particular description of this phenomenon was given by L. in 
an earlier letter (7 April 1674) published—in part only—in Phil. Trans., 
Vol. IX, p. 23. The more famous description of the “blood and guts in the 
louse” by Swammerdam was not published until long after this date. 
* See note 2 on p. 141. 
* No date is here recorded. 
