ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
157 
Btaining fluid : — -O' 75-1 -0 parts hematoxylin ; 90 parts water ; 10 parts 
alcohol ; 1 part lithium carbonate. 
At the end of 24 hours they may be removed, washed in water, and 
are then ready for the differentiating bath : — borax, 2 parts ; ferrocyanide 
of potash, 2-5 parts; distilled water, 200 parts. 
Some experience and great care are requisite in differentiating the 
sections, but witli patience and judgment they can be developed with 
as much precision as the photographer displays in bringing out the 
light and shadows of a dry plate. The sections should be placed in the 
bath singly, so that each one may bo removed as soon as it is differen- 
tiated. The length of time required is variable, depending upon the 
thickness of the sections. The general outlines of tho white and grey 
matter should be known beforehand, and if pathological the seat of tho 
lesion, so that as soon as the contour of the different regions becomes 
distinct, the sections may be immediately removed from the bath. 
Over -development destroys the sections, and hence as soon as they are 
removed from the bath they must bo thoroughly washed in water for 
12, 18, or 24 hours, to arrest all further development. They are then 
dehydrated in strong alcohol, cleared iu Weigert’s clearing mixture: — 
xylol, 3 parts ; carbolic acid, 1 part ; sulphate of copper, enough to cover 
the bottom of the bottle ; and mounted in balsam. 
The grey matter, connective tissue, and vascular walls are stained 
light brown ; the ganglion cells, dark brown ; while the white matter 
takes on a blackish-blue or purplish-blue tint. 
The Pal Method. — This method, which is merely a modification of 
the Weigert method, was described by Prof. Pal, of Vienna, in ‘Wiener 
Medizinische Jahrbucher,’ 1887, p. 589. The preliminary preparation 
of the sections is the same as with the Weigert method ; but with care 
and dexterity the imbedding in collodion may be dispensed with, as they 
are not rendered so friable and brittle. They are immediately placed 
in Weigert’s staining fluid, to which has previously been added three to 
five drops of a saturated solution of lithium carbonate for every 10 ccm. 
of the stain used. After five or six hours they may be removed and 
carefully washed in water to which some of the carbonate of lithium 
solution has been added. They are now placed for ten or fifteen seconds 
in a 1/4 per cent, solution of the permanganate of potash, rinsed in 
30 per cent, alcohol, and placed in the differentiating bath : — oxalic acid, 
1 part ; sulphite of soda, 1 part ; distilled water, 200 parts. 
The same hints regarding the differentiation of the sections as given 
under the Weigert method are applicable in this method. Should the 
sections be very slow in developing, they may be replaced in the 
permanganate of potash solution and the process continued as before. 
After they have been sufficiently differentiated they should be carefully 
washed in water for 24 hours, dehydrated in strong alcohol, cleared in 
Weigert’s clearing mixture, and mounted in balsam. 
The medullary nerve-fibres are stained light blue, the neuroglia, 
connective tissue, and vessel walls are rendered white or yellowish- 
white, while the ganglion cells become transparent. To stain these 
cells, after the development has been arrested by the water-bath, the 
sections should be placed in a picrocarmine stain for a short time, and 
the process completed in the ordinary way. To stain the nuclei, tho 
