Squire’s Fluid.—(1) Mix 95 parts of glycerine with 5 parts of hydrochloric acid; used for softening teeth. (2) Use a 4 per cent. aqueous solution of arsenic acid at a temperature of 30° to 40° C. After softening tissues in this solution, keep them in alcohol.
Waldeyer.—To a 0·1 per cent. solution of palladium chloride, add one-tenth its volume of hydrochloric acid.
HARDENING, FREEZING, AND EMBEDDING.
Altmann (Fixing Solution).—A mixture of equal parts of 5 per cent. potassium bichromate solution and 2 per cent. osmic acid.
Alcohol.—Strengths of alcoholic solutions, as given by Squire, will be found of practical value. Absolute alcohol (sp. gr. O·797) containing about 98 per cent. of ethylic alcohol is taken as the basis in most instances. Alcohol of 90 per cent. (sp. gr. 0·823) is prepared by mixing 14 volumes of absolute alcohol and 1 volume of distilled water; 84 per cent. alcohol (sp. gr. 0·838) is rectified spirit B.P.; 70 per cent. alcohol (sp. gr. 0·872) may be obtained by adding 1 volume of distilled water to 3 volumes of absolute alcohol, 6 volumes of rectified spirit, or 4 volumes of methylated spirit; 50 per cent. alcohol (sp. gr. 0·918) is prepared by adding 4 volumes of distilled water to 5 volumes of absolute alcohol, 3 volumes of water to 5 volumes of rectified spirit, or 3·5 volumes of water to 5 volumes of methylated spirit. Absolute alcohol, 75 C.c., mixed with acetic acid, 25 C.c., serves as an excellent fixing agent for nuclei. Immerse tissues in it for 6 to 12 hours, then transfer to 90 per cent. alcohol until hardened, afterwards preserving in 70 per cent. alcohol till wanted.
Betz’s Hardening Fluid.—A mixture of equal parts of sulphuric ether and alcohol. This is used for hardening the brain of insects prior to cutting sections.
Cole’s Freezing Process.—Dissolve picked gum acacia, 4 ozs., in distilled water, 6 ozs., and to each 5 parts of the resulting mucilage add 3 parts of syrup made by dissolving loaf sugar, 1 lb., in distilled water, 1 pint. To each ounce of the medium add 5 grains of pure carbolic acid, and soak the tissues in it prior to freezing. For tissues liable to come to pieces, mix 4 parts of syrup with 5 of mucilage.
Flemming’s Fixing Solution.—Osmic acid (1 per cent. solution), 80 C.c.; chromic acid (10 per cent. solution), 15 C.c.; glacial acetic acid, 10 C.c.; distilled water, 95 C.c.
Fol’s Fixing—Osmic acid (1 per cent. solution), 4 C.c.; chromic acid (10 per cent. solution), 5 C.c.; glacial acetic acid, 10 C.c.; distilled water, 181 C.c.
Fischer’s Imbedding Mass.—Dissolve 15 parts of transparent soap in 17·5 parts of 96 per cent. alcohol.