2. After-harden in saturated watery picric solution 4-8 days: or combine 1 and 2 by using formol 10 cc. with 90 cc. saturated picric acid solution.
3. Place in a 5 per cent aqueous solution of ammonium bichromate, 4-7 days at 37°C., changing solution 011 second day; or 3-4 weeks at room-temperature.
4. Without washing, harden in alcohol; imbed in celloidin or paraffin; cut.
5. Place sections in ¼ per cent aqueous solution of potassium permanganate, 15-30 minutes.
6. Wash in water.
7. Immerse in 5 per cent aqueous oxalic acid, 5-30 minutes.
8. Wash in several changes of water.
9. Stain in following solution, 1-several days: Hæmatoxylin 0.1 grm., 10 per cent phosphotungstic acid 20 cc., hydrogen peroxide 0.2 cc., water 80 cc.
10. Wash rapidly in water.
11. Differentiate in freshly prepared 30 per cent alcoholic solution of ferric chloride, 5-20 minutes.