The spirochætes are dark brown to black. Silver precipitates occur chiefly in the outer portions of the tissue. The reticulum is brown; other parts of the tissue are yellowish. Levaditi’s more recent modification of this method does not give so good results as the original.
Schmorl’s Staining of Sections with Giemsa’s Stain.
1. Fix in 10 per cent formol. Cut very thin sections on freezing-microtome.
2. Place the sections in a staining dish containing a measured amount of distilled water. To each cc. of water add one drop of Giemsa’s stain. Use clean glass-needles to manipulate the sections. After 1 hour transfer sections to a fresh solution, in which they are left 5-12-24 hours.
3. Wash quickly in a concentrated solution of potassium alum, then quickly in water.
4. Mount in glycerin-gelatin; or dry on the slide until nearly perfectly dry, then xylol, and balsam, or cedar oil. Alcohol must not be used.
II. THE STAINING OF PATHOGENIC YEASTS AND MOULDS IN SECTIONS.
1. Blastomycetes. The parasites of blastomycetic dermatitis can be demonstrated unstained in pus treated with a weak sodium hydroxide. In sections they are easily found after treatment with ordinary staining methods. The various modifications of the Romanowsky method, or other methylene-blue-eosin staining, give better staining of the parasite than can be obtained by hæmatoxylin and eosin.
2. Oïdium Albicans. Staining with Weigert-Gram’s and lithium-carmine gives beautiful preparations.
3. Moulds. These are best examined in the unstained condition, by treating the material with equal parts of alcohol and ether, followed by a 3 per cent potassium hydroxide solution. The organisms and spores are brought out distinctly. Löffler’s methylene-blue may be used for staining. In the case of sections stain 1-2 hours and contrast with eosin. For the examination of hairs or horny scales for fungi, Unna’s method may be used:—