7. Cut.
8. Stain in Weigert’s iron-hæmatoxylin, 24 hours.
9. Wash in water, 30 minutes or longer.
10. Differentiate in borax-potassium ferricyanide (potassium ferricyanide 2.5 grms., borax 2 grms., water 100 cc.) until the gray substance appears yellow to white. Control under microscope.
11. Wash thoroughly in water.
12. Dehydrate in absolute alcohol; clear in xylol; mount in balsam.
Myelinated fibres, blue-black, upon a colorless or light yellow background; red blood cells may be blue-black. Weigert’s method is better than any of the numerous modifications.
B. Orr’s Osmic-Acid Method.
1. Place fresh tissue from cerebral cortex or cord, not more than ⅛ inch in thickness, in 1 per cent acetic, 2 cc., and 2 per cent osmic acid 8 cc., for 48 hours. If mixture is darkened at end of 24 hours, renew.
2. Transfer to 10 per cent formol for 3 days, in order to complete reduction and hardening.