A Tungstate Modification of the Golgi-Cox Method

Pieces of fresh nervous tissue 4-5 mm thick are put into the following solution: HgCl₂, 1 gm; K₂Cr₂O₇, 1 gm; K₂CrO₄, 0.8 gm; K₂WO₄ (or Na₂WO₄), 0.5 gm; distilled water 100 ml. They are kept undisturbed in the dark at room temperature for 20-30 days, then transferred to the following alkaline solution: LiOH (or NaOH), 1 gm; KNO₃, 15 gm; distilled water, 100 ml. After 12-24 hr in this solution they are washed for 12-24 hr in several changes of distilled water. (If sodium hydroxide was used, 0.5 ml of acetic acid should be added per 100 ml of wash water.) Embedding in celloidin follows dehydration. Sections are dehydrated in 3 parts of absolute alcohol and 1 part of chloroform, cleared in iodobenzene and mounted with a cover slip using a mounting medium with a refractive index around 1.61. The use of tungstate improves the general results and allows especially successful impregnations in very young animals, when the usual technic fails.