Mayer’s Carmalum.—Dissolve 1 Gm. of carminic acid and 10 Gm. of alum in 200 C.c. of distilled water; decant, or filter, and add a few crystals of thymol, 0·1 per cent. of salicylic acid, or 0·5 per cent. of sodium salicylate. A weaker solution contains 3 to 5 times as much alum and 5 times as much water.
Merbel’s Carmine and Indigo Fluids (give a blue and red stain, and are very selective).—To prepare the red fluid, take—Carmine, 2 dr.; borax, 2 dr.; distilled water, 4 ozs. For the blue fluid, take—Indigo carmine, 2 dr.; borax, 2 dr.; distilled water, 4 ozs. Mix each in a mortar, and allow it to stand, then pour off the supernatant fluid. If the sections have been hardened in chromic acid, picric acid, or a bichromate, they must be washed in water till no tinge appears. Place them in alcohol for fifteen or twenty minutes, then in the two fluids mixed in equal proportions, after which wash them in a saturated aqueous solution of oxalic acid, where they should remain a rather shorter time than in the staining fluids. When sufficiently bleached, wash them in water, to get rid of the acid, then pass them through spirit and oil of cloves, and mount in balsam or dammar.
Mitrophanow’s Gold Process for Prickle-Cells and Intercellular Canals.—Wash the tail of an axolotl larva with distilled water, place for an hour in a watch-glassful of 0·25 per cent. solution of gold chloride, containing 1 drop of hydrochloric acid; wash, and reduce in a mixture of 1 part of formic acid with 6 parts of water.
Mitrophanow’s Maceration Method for Epithelium.—Fix the embryo for 15 minutes in 3 per cent. nitric acid; then place for an hour in a mixture of alcohol, 1 volume, and water 2 volumes, and finally treat with stronger alcohol for 24 hours to separate the epidermis.
Müller’s Berlin Blue for Injections.—Precipitate a concentrated solution of Berlin blue by means of 90 per cent. alcohol. The precipitate is very finely divided, whilst the fluid is perfectly neutral and much easier to prepare than that of Beale.
Neilsen’s Solution of Methyl Violet.—Dissolve fuchsine, 1 part, in alcohol, 10 parts, and add a 5 per cent. watery solution of carbolic acid, 100 parts.
Neisser’s Double-Staining for Spore-Bearing Bacilli.—Cover-glass preparations are immersed for 20 minutes in fuchsine aniline water (concentrated alcoholic solution of fuchsine, 11 C.c.; absolute alcohol, 10 C.c.; aniline water, 100 C.c.; then heat to 80° or 90° C.; next rinse in water, alcohol, or weak acid, according to the nature of the bacilli, counterstain with aqueous solution of methylene blue, rinse in water, dry and mount in balsam). The spores are stained red and the rest of the bacilli blue.
Nissl’s Fuchsine Stain for Nerve Cells.—(1) Fresh material in pieces measuring 1 C.c. are hardened in a “chromic solution in 70 per cent. alcohol” for 2 days, then transferred to absolute alcohol for 5 days, and afterwards cut. Stain the sections singly in a saturated solution of fuchsine, warming in a deep watch-glass until vapours begin to be given off. Next plunge the section into absolute alcohol for 1 or 2 minutes, then place it on a slide, flood with clove oil, and when no more colour is given off, drain and mount in balsam.
Ohlmacher’s Formaldehyde Staining.—Formalin in a 2 to 4 per cent. solution is used as a mordant for tar colours. The tissues may be mordanted separately by treatment for 1 minute or longer, or the formalin may be added to the stain. Dissolve 1 Gm. of fuchsine in 10 C.c. of absolute alcohol, and add to 100 C.c. of 4 per cent. formalin solution. Or, add saturated alcoholic solution of gentian violet or methyl violet 5 B. to the formalin solution, in the proportion of 1:10. In the case of methylene blue, dissolve 1 G.m. in 100 C.c. of the formalin solution. Sections stain in half a minute, and are said to resist alcohol much more than if formalin were not used.
Oppitz’s Silver Staining.—Reduction is very rapidly effected by placing the preparations for 2 or 3 minutes in a 0·25 to 0·5 per cent. solution of chloride of tin.