Tue MIcRoscoPe. 83 
For secretory glands in general, as the pancreas, salivary 
glands, etc., it is best to use absolute alcohol at once. The hard- 
ening is frequently complete in twenty-four hours, and although 
there is much shrinking of the tissue yet the sections will take 
staining very readily. 
POTASSIC BICHROMATE SOLUTION. 
Many prefer a 2 per cent. solution of this regent to Miiller’s 
fluid. It is used in the same way as recommended for that 
fluid. 
AMMONIA BICHROMATE SOLUTION. 
A two per cent. solution of this is preferred by some to the 
potash solution. It is similarly employed. It is especially 
mentioned as a valuable hardening agent for the nervous struc- 
tures. 
CHROMATE OF AMMONIUM. 
A five per cent. solution is used. It is especially recom- 
mended for showing the rods of Heidenhain in the lining cells 
of the uniniferous tubules. It is only necessary that small por- 
tions of the cortical substance of a kidney be placed in the 
solution for forty-eight hours. It is a valuable reagent for 
showing the “ goblet cells” of Klein. A piece of smal] intes- 
tine is placed in the solution for forty-eight hours, after which 
it is well washed in water and some of the mucous membrane 
removed and mounted in glycerine jelly. 
CHROMIC ACID. 
Chromic acid may be used in solution with water. A 1 per 
cent. solution is made and this is reduced to a4 or $ per cent. 
solution when required for use. 
CHROMIC ACID AND ALCOHOL. 
Make a ¢ per cent solution of chromic acid and to one part 
of this solution add two parts of alcohol. It should be made 
only when required for use. It is a generally useful solution 
and hardens tissue in from a week to ten days. As soon, how- 
ever, as the tissue becomes tough, yet retaining its elasticity, it 
is washed in water and transferred to alcohol. 
The fluid should be changed the second day. 
