Koch’s Copal.—Stain small pieces of material in bulk, and dehydrate with alcohol, then immerse in a thin solution of copal in chloroform. Evaporate with a gentle heat until the solution is so far concentrated as to draw out into threads that are brittle on cooling. Then remove the objects and leave on a tile for a few days to dry. Sections may then be cut by means of a fine saw. If objects are imbedded unstained, remove copal from sections by soaking in chloroform, decalcify if necessary, and stain.
Eulenstein’s Cement.—Mix equal parts of Brunswick black and gold size with a very little Canada balsam.
DECALCIFYING AND BLEACHING.
In the case of bony structures, or tissues so impregnated with calcium salts, the material should be decalcified by an acid capable of dissolving out the mineral matter. Hydrochloric acid with alcohol is in more general use. The older the bone the stronger will be the acid required, nitric with alcohol and chromic acid. Picric acid is preferred for fœtal bone.
Andeer, J. J., finds an aqueous solution of phloroglucin acts as a powerful decalcifying agent on the bones of animals, but is without action on the most delicate organic tissue. If treatment with hydrochloric acid be employed as well, the residual “ossein” will be without a trace of either calcium phosphate or carbonate.
Ebner’s Fluids.—(1) Mix 100 C.c. of cold saturated aqueous solution of sodium chloride, 100 C.c. of water, and 4 C.c. of hydrochloric acid. Preparations are placed in the fluid, and 1 to 2 C.c. of hydrochloric acid added daily until they are soft. (2) Mix 2·5 parts of hydrochloric acid (sp. gr. 1·16) with 500 of alcohol (90 per cent.), 100 of water, and 2·5 of sodium chloride.
Fol’s Liquid.—Mix 70 volumes of 1 per cent. chromic acid, 3 of nitric acid, and 200 of water.
Mayer’s Desilification Process.—Place the objects in alcohol contained in a glass vessel coated internally with paraffin, then add hydrofluoric acid drop by drop until desilification is complete, avoiding the fumes meanwhile.
Marsh’s Chlorine Method.—Chlorine is generated in a small bottle by treating crystals of potassium chlorate with strong HCl., and the gas is led through a piece of glass tubing, bent twice at right angles, to the bottom of a bottle containing the sections immersed in water.
Ranvier’s Fluid.—Use 50 per cent. hydrochloric acid with the addition of sodium chloride to counteract its swelling action.