me anes Microscopy. eT 
“airing ’’ is not required with marine animals, as with them the color 
differentiation is completed in the staining fluid. 
In the case of marine animals the methylenblue is dissolved in sea- 
water. It dissolves less readily than in fresh water, and owing to this 
weak solubility it is liable to form a fine granular or crystalline pre- 
cipitate on the surface of the preparation. As a large part of the 
dissolved, staining substance is lost by filtering, it is best to prepare it 
fresh each time, and to allow it to settle, so that the clear fluid can be 
turned off for use. In the case of Nereis the nerve-cord is not 
obscured by a thick opaque sheath, and hence it is only necessary to 
open the dorsal wall lengthwise and spread it out flat in order to apply 
the stain. 
Vasale’s Modification of Weigert’s Method:*—The pieces 
of the nervous system to be prepared are hardened in Miiller’s fluid or 
in bichromate of potash, and then, either with or without washing, left 
in alcohol until they are wanted for sectioning. For staining, the three 
following fluids are required : 
1. Hematoxylin 1 g., dissolved in 100 g. water by heating. 
2. Neutral acetate of copper, saturated, filtered solution. 
3. Borax 2 g., ferricyanide of potash 2% g., dissolved in 300 g. 
water. 
The sections taken from alcohol are placed in solution 1 for three 
to five minutes; then for the same time in solution 2, in which they 
become black. They are next washed quickly in water and put into 
solution 3, which is stirred, and in which the ganglion-cells, neu- 
roglia, and the degenerated parts are quickly discolored, while the 
medullated fibers remained stained dark violet. Finally the sections 
are washed in water and quickly placed in absolutealcohol. They are 
cleared with cardo/-xy/ol (three parts xylol to one of liquid carbolic acid), 
and mounted in xylol balsam. This clearing mixture hasthe advantage 
that it does not shrink sections inclosed in celloidin. A contrast-stain 
may be obtained if the sections, after being washed, are treated with 
alum carmine or picrocarmine, or according to Pal’s method. 
Upson’s Gold-Staining Method for Axis-Cylinders and 
Nerve-Cells.°—Pieces of the central nervous system are hardened in 
potassium bichromate, beginning with one per cent. and increasing to 
2% m cent. They are left in this fluid in the dark from four to six 
tRivista sperimentale di Freniatria e r Medicina legale, Vol. XV., 1889., p- son's. 
Zeitschr. J. Wiss. Mikr., VIL., 4, 1891, p. 5 
5A. Mercier. “ Die Upson'schen caus fiir Achseneylinder und Zellen (Gold) , 
Färbung. Sni Wis Mikr., VII., 4, P- 474, 1891. 

