150 deg.; when it cools, it will
become hard and crystalline. Dissolve this in benzole, and use in the
same way as glycerine.

Dammar is now used as a substitute for Canada balsam. By its use the
tissues are rendered more transparent. To prepare it, dissolve one-half
ounce of Dammar rosin and one-half ounce of gum mastic in three ounces of
benzole, and filter. This may be used to mount unsoftened bone and tooth,
hair, brain, and spinal column, and most tissues that have been hardened
in alcohol or chromic acid, which require to have their transparency
increased.

Glycerine is not adapted for white fibrous tissue or blood vessels,
unless they have been hardened in chromic acid, as it causes the white
fibers to swell up and lose their normal features. Sections of liver,
lung, skin, and alimentary canal show better in glycerine unless they
have been stained.

Farrant's solution may be substituted for glycerine in many instances,
because of its feebler tendency to render the tissues transparent. It
consists of equal parts of gum arabic, glycerine, and a saturated
solution of arsenious acid. In mounting preparations with this medium,
the covered object should be allowed to lie a day before the varnish is
applied, so that the cover may be fixed, and thereby prevented from being
displaced. Rectified spirits may be used for mounting softened bone and
tooth, and naphtha and creosote are useful for preserving urinary casts.

When the section is mounted in Canada or Dammar balsam, no cement is
required, but for all other preservative media the margin of the cover
must be covered with cement. To do this, dry the edges of the cover
thoroughly with bibulous paper, and paint a layer of gold size, allowing
it to overlap the cover an eighth or sixteenth of an inch, then cover
this with white zinc cement.

_Preparation for mounting the different tissues_.--To obtain a section of
bone or tooth requires a grinding down of the tissue until it is so thin
as to be transparent. A section should first be cut as thin as possible
by a fine saw. It should be attached by the flattest side to a piece of
glass, and then ground down by a grindstone or by very fine emery, on a
perfectly flat piece of lead. When sufficiently thin and transparent,
mount in rectified spirits or Dammar. Sections of the tongue may be made
by embedding in paraffin, and mounted in Farrant's solution or glycerine.

Sections of the stomach may also be made by embedding in