Hoyer’s Silver Stain.—Add ammonia to a solution of silver nitrate of known strength, until the precipitate formed just re-dissolves, then dilute the solution until it contains 0·75 to 0·50 per cent. of the salt.
Kaiser’s Bismarck Brown Stain. Sections are stained for 48 hours, at a temperature of 60 C., in a saturated solution of Bismarck brown in 60 per cent. alcohol, and washed out in 60 per cent. alcohol containing 2 per cent. of H.C.L., or 3 per cent. of acetic acid.
Kaiser’s Nerve Stain.—This is a modification of Weigert’s process. The material is hardened in Müller’s solution for 2 or 3 days, then cut into slices 2 to 4 Mm. thick, and treated with the solution for 5 or 6 days more. Subsequently immerse in Marchi’s solution for 8 days, then wash, pass through alcohol, and imbed in celloidin. Sections are mordanted for 5 minutes in the following mixture:—Solutions of ferric chloride, 1 part; distilled water, 1 part; rectified spirit, 8 parts. Next wash in Weigert’s hæmatoxylin, and warm in a fresh quantity of the same for a few minutes, wash with water, differentiate in Pal’s solution, and neutralise the oxalic acid by washing in water containing a little ammonia.
Kaiser’s Stain for the Spinal Cord.—Sections are stained for a few hours in solution of náphthylamine brown, 1 part, in water, 200 parts, and alcohol, 100 parts. Afterwards wash with alcohol and clear with origanum oil.
Kallin’s Neurological Method.—Dissolve hydroquinone, 5 Gm., sodium sulphite, 40 Gm., and potassium carbonate, 75 Gm., in 25 Gm. of distilled water. At the time of using, dilute this solution with one-third to one-half its bulk of absolute alcohol; immerse sections of silvered material for several minutes until reduction is complete. Then place them in 70 per cent. alcohol for 10 to 15 minutes, and subsequently leave in aqueous solution of sodium hyposulphite (1:5) for 24 hours or more. Finally dehydrate and mount. Carmine may be used as an afterstain.
Kleinenberg’s Solution (Improved Formula).—Hæmatoxylin, 2½ Gm.; crystallised calcium chloride, 20 Gm. in 10 C.c. of distilled water; alum, 3 Gm. in 16 C.c. of distilled water; rectified spirit, 240 C.c. Dissolve the calcium chloride and alum in their respective quantities of water by the aid of heat; mix the solutions and immediately dilute with rectified spirit; after an hour filter and add the hæmatoxylin. This makes a good working solution which keeps well. Of course it contains the alumina in solution, not as alum but aluminium chloride. If in special cases the colour is considered too strong, the dilution (when staining in bulk) must be made with some of the solution to which hæmatoxylin has not been added.
Koch’s Method for Staining Flagella.—Immerse cover-glass preparations in a 1 per cent. aqueous solution of hæmatoxylin, then transfer to a 5 per cent. solution of chromic acid or to Müller’s fluid; dry and mount in balsam.
Koch-Ehrlich, Bacilli.—Place sections, or cover-glass preparations, for at least 12 hours in gentian violet, or fuchsine aniline water (aniline water, 100 C.c.; concentrated alcoholic solution of gentian violet, or fuchsine, 11 C.c.; absolute alcohol, 10 C.c.), then immerse in a mixture of pure nitric acid (sp. gr. 1·42), 10 C.c., and distilled water, 30 C.c., for some seconds. Rinse in 60 per cent. alcohol for a few minutes, and then counterstain with vesuvine (vesuvine, 0·5 Gm.; rectified spirit, 20 C.c.; distilled water, 80 C.c.) after gentian violet; or methylene blue (methylene blue, 0·25 Gm.; rectified spirit, 20 C.c.; distilled water, 80 C.c.) after fuchsine. Finally rinse in water, dehydrate, clear, and mount in balsam. According to Squire, who points out that nitric acid is apt to injure delicate sections, Watson Cheyne recommends that sections should be transferred from fuchsine aniline water to distilled water, then rinsed in alcohol, and placed in the following contrast stain for 1 or 2 hours:—Saturated alcoholic solution of methylene blue, 20 C.c.; distilled water, 100 C.c.; formic acid (sp. gr. 1·2), 1 C.c.
Kühne’s Carbolic Methylene Blue.—Rub up 1·5 Gm. of methylene blue with 10 C.c. of absolute alcohol, and add 100 C.c. of a 5 per cent. aqueous solution of carbolic acid.
Kühne’s Methyl Violet Solution.—Dissolve 1 Gm. of methyl violet in 90 C.c. of distilled water and 100 C.c. of alcohol.