Page 193 - My FlipBook

MICROSCOPICAL PHENOMENA OF DECAY. 167
" Take a freshly-extracted tooth and grind it down with a
coarse cornndum-wheel to a pretty thin hunella, according as a
transverse or a longitudinal section is desired. This lamella
should then be ground on one side perfectly even on a fine stone,
and then polished on the same side upon leather, coating with
some fine polishing-powder until no rays are visible on this side
anjnvhere. The lamella should then be cemented with the pol-
ished side down on a glass slide, such as is used for putting up
microscopical preparations, with some thick Canada balsam,
which is easily softened by heating, and then firmly pressing the
lamella against the glass. Around the lamella are cemented
some exceedingly thin pieces of covering-glasses, as used in
microscopy.
" Practically it is best to cement on the other side of the glass
a piece of cork, so that tlie slide can be easily managed during
the further process of grinding. The lamella is then ground In-
hand on a fine and perfectly flat stone until all the thin cover-
ing-glasses are evenly touched. By this process the lamella is
made of an equal thickness, with the covering-glasses cemented
around it.
" The cover-glass pieces are then removed and the lamella
ground still thinner; when thin enough, it generally detaches
itself. All this grinding must be done with water on a water-
stone. The final step is to polish it on this newly-ground side.
" The exceedingly thin plate procured in this manner should
then be washed in alcohol, and every particle of polishing-pow-
der brushed ofi:" with a fine camel's-hair brush. The ground sec-
tion is now ready for mounting. For this purpose it is placed
in absolute alcohol for five minutes or longer, by which Qxery
trace of water is removed. It is then transferred to oil of cloves
to clear it; then placed on a clean glass slide, a drop of Canada
balsam put on it, and covered with a thin cover-glass. The
preparation is now finished and ready for examination under
the microscope."
Charters "White (" Elementary Microscopical Manipulation")
recommends rubl)ing down the sections between two plates of
ground glass, with the addition of some pumice-powder and
w^ater ; a method which is said to give very good results.