Klein’s Hardening.—Mix 1 C.c. of 10 per cent. chromic acid solution with 60 C.c. of water, and add 30 C.c. of 90 per cent. alcohol.
Müller’s Fluid Formula, see page 288.—This solution is sometimes mixed with one-third its volume of 90 per cent. alcohol, its hardening action being then much more rapid.
Rabl’s Hardening Fluid.—Chromic acid solution (10 per cent.), 7 C.c.; water, 200 C.c.; formic acid (sp. gr. 1·2), 5 drops.
Rollett’s Freezing Process.—Small portions of tissue placed on the stage of microtome, after immersion in the white of an egg, then frozen and cut with a very cold knife.
Ryder (Double Embedding).—After the celloidin bath, soak objects in chloroform, then remove into a mixture of chloroform and paraffin, heated to not more than 40° C., and finally into a bath of pure paraffin.
Stricker (Imbedding Mass).—Prepare the objects in alcohol and imbed in a concentrated solution in gum arabic in a paper case, then throw the whole into alcohol and cut after 2 or 3 days.
Webb (Dextrin Freezing).—A thick solution of dextrin (1:40) in aqueous solution of carbolic acid is used for imbedding, and subsequently frozen.
MOUNTING MEDIA.
Sections are usually mounted in balsam, dammar, glycerine, &c., but it is not a necessity that the cover-glass should be fixed or cemented down. Some cements (caoutchouc by preference) should be employed when glycerine or aqueous (Farrant’s) media are used.
Alleger’s Gelatine Process.—Add a few drops of formalin to each gramme of 0·5 to 1 per cent. gelatine solution. After mounting the section in this, apply heat to the slide until the paraffin is softened, and allow the superfluous gelatine to drain from the edge of the slide.