Microscopy. 859 
Preparation.—1. Alcohol supplies the best means of hardening, 
as it well preserves the color and form. If other reagents are 
employed, such as zinc chloride, Miiller’s fluid, etc., the prepara- 
tion must lie in alcohol awhile before further treatment. 
. The hardened preparation is removed from the alcohol, made 
dry superficially by careful application of soft linen, and then coated 
with a thin layer of celloidin, applied with a fine brush. The cel- 
loidin is dissolved in a mixture of equal parts of strong alcohol 
and ether, as for imbedding. The furrows are not to be filled with 
the celloidin solution, but the walls must be carefully and thor- 
oughly painted. In order to keep them open during the process o 
hardening, it is well to fill them with cotton or with blotting-paper. 
ithin five or ten minutes the celloidin dries to a thin, trans- 
parent, tough membrane, which protects the preparation and gives 
it greater firmness. 
Dry Preparations of THE BRAtN.—The method of impreg- 
nating the brain with paraffine was first employed by Fredericq,? 
in 1878. Schwalbe* adopts essentially the same method for the 
human brain, proceeding as follows : 
Hardened in zinc chloride or in alcohol. 
_2. After removing the membranes, cut into a number of suitable 
pieces, as it is not advisable to impregnate the brain in toto. — 
3. After dehydrating in 96 to 97 per cent. alcohol, soak in tur- 
Pentine until completely saturated. 
Impregnate with soft paraffine, kept at 60°C. (five to eight 
5. The paraffinized preparation is placed on a layer of cotton to 
cool, care being taken to give it such a position as to avoid defor- 
- mation, 
' Michael v. Lenhossék. {‘‘Celloidinbehandlung des Gehirns zur 
rr oan iia Demoustrations-praiparaten.”’ Anat. Anz. ii., 3, p. 77. 
t d . 
: Bull. de l’ Acad. roy. de Belg., 2 ser., xl., June, 1876. 
Anat. Anz., i., No. 12, p. 322, Nov., 1886. 
