O f A n i m a l c u l a i n I n f u s i o n s , &c .
Thefe require little or no preparation. The firft objea is to
procure them, the fecond to render them vifible by the microfcope.
A few obfervations, however, may be o f ufe. Many
drops o f water may be examined before any can be found ; fo
that if the obferver be too hafty, he may be eafily difaypointed,
though other parts of the fame water may be fully peopled by
them. '
The furface of infufed liquors is generally covered with a thin
pelicule, which is eafily broken, but acquires thicknefs by Handing
; the greateft number o f animalcula are generally to be found
in this fuperficial film.
In fome cafes it is neceffary to dilute the infufions; but this is
always to be done with diftilled water, and that water Ihould be
examined in the microfcope before it is made ufe of: the neg-
le a o f this precaution has been a fource o f many errors.
Animalcula are in general better obferyed when the water is a
little evaporated, as the eye is not confufed, nor the attention
diverted by a few objeas. T o feparate one or two animalcula
irom the reft, place a fmall drop o f water on the glafs near that
o f the infufion ; make a fmall neck, or gutter, between the two
drops with a pin, which will join them together ; then the inftant
you perceive that an animalculum has traverfed the neck or gutter,
and entered the drop, cut off the communication between the
two drops.
T o
To procure the eels in pafte, boil a little flour and water, till
it comes to the confiftence o f fuch a pafte as is ufed by the bookbinders
; expofe it to the air in an open veffel, and beat it together
from time to time, to prevent the furface thereof growing
hard or mouldy : after a few days it will turn four ; then, if it be
examined with attention, you will find myriads o f eels on the
furface.
T o preferve thefe eels all the year, you mnft keep the furface
of the pafte moift, by putting a little water or frelh pafte from
time to time to the other. Mr. Baker advifes a drop or two o f
vinegar to be put into the pafte now and then. The continual
motion o f the eels, while the furface is moift, will prevent the
pafte getting mouldy. Apply them to the microfcope upon a
flip of flat glafs, firft putting on it a drop o f water, taken up
by the head o f a pin, for them to fwim in.
T o make an infufion o f pepper. Bruife as much common
black pepper as will cover the bottom of an open jar, and lay it
thereon about half an inch thick; pour as much foft water in the
veffel as will rife about an inch above the pepper. The pepper
and water are then to be well {hook, together; after which they
muft not-be ftirred, but be left expofed to the air for a few days,
when a thin pelicule will be formed on the furface of the water,
containing millions o f animalcula.
The obferver fhould be careful not to form a judgment o f the
nature, the ufe, and the operations of fmall animalcula, from
ideas which he has acquired by confidering the properties of larger
animals: for, by the afliftance o f glafles, we are introduced as it