the fame with the under fide. When the {kin is taken off on
both fides, wafh out the pulpy matter, and the fibres will be exhibited
in a beautiful manner. By flitting the ftalk you may
feparate the anatomized leaf into two parts. The fkins that are
peeled from the fibres will alfo make a very good objefit. The
autumn is the beft feafon for the foregoing operation, as the fibres
o f the leaves are much ftronger at that feafon, and lefs liable to
break.
Ores and minerals {hould all be carefully wafhed and brulhed
with a fmall brufii, to remove any extraneous matter that may adhere
to them. Shells may be ground down on a hone, by which
their internal ftru&ure will be difplayed.
T o VIEW THE CIRCULATION A N D EXAMINE THE PARTICLES
of the blood. The principal point the obferver mull aim at,
in order to view the circulation o f the blood, is to procure thofe
fmall animals or infefts that are moft tranfparent, that by feeing
through them he may be enabled to difcover what pafles within
them. The particular kinds beft adapted for the purpofe will be
enumerated in the defcriptive catalogue at the end o f this work.
I f a fmall eel is ufed for this purpofe, it muft be cleanfed from
the flime which covers i t ; after which it may be put either in the
fifh-pan, or a glafs tube filled with water, and then placed under
the microfcope. I f the eel is fmall enough, the circulation may
be viewed in the moft fatisfaftory manner. Leeuvenhoeck has
given, in his 1 12th epiftle, an accurate defcription o f the blood-
veflels in part o f the tail o f an eel. The fame figure may alfo be
eenin my fa ther’s Treatife on the Microfcope. The tail o f any
other
other fmall filh may be applied in the fame manner, or tied on a
flip of flat glafs, and be thus laid before the microfcope.
Flounders, eels, and gudgeons, are to be had almoft at any time
in London.— N. B. By filling the tube with water, when an eel is
ufed, it will in a great meafure prevent the fliminefs o f the eel
from foiling the glafs.
To view the particles o f the blood, take a fmall drop o f it
when warm, and fpread it as thin as poflible upon a flat piece of
glafs. By diluting it a little with warm water, fome of the larger
globules will divide from the lmaller, and many o f them will be
fubdivided into fmaller ones : or a little drop o f blood may be
put into a capillary tube o f glafs, and be then prefented before
the microfcope. Mr. Baker advifes the mixing the blood with
a little warm milk, which, he fays, will caufe the unbroken particles
to be very diftinftly feen ; but the moft accurate obferver o f
thefe particles was Mr. Hewfon, and he fays, they have been
termed globules with great impropriety, being in reality flat
bodies. When we confider how many ingenious perfons have
been employed in examining the blood with the beft microfcopes,
it appears furprizing that the figure o f the particles fhould be
miftaken; but the wonder is leflened when we reflect how many
obvious things are overlooked, till our attention is particularly
direfled towards them ; and befides, the blood in the human fub-
jeft, and in quadrupeds, is fo full of thefe particles, that it is
with great difficulty they can be feen feparate until the blood is
diluted. It was by difcovering a proper method to effeft this that
Mr. Flewfon was indebted for his fuccefs. He diluted the particles
with ferum, in which they would remain undiffolved, and as he
could dilute them to any degree w ith die ferum, he could eafily
■ y 2 examine