426 HISTOLOGICAL TECHNIQUE. 



4. Rinse in distilled water. 



5. Differentiate in equal parts of glacial acetic acid and distilled 

 water. 



6. Wash thoroughly in distilled water. 



7. Dehydrate in absolute alcohol. 



8. Clear in xylol, carbol-xylol, or some essential oil. 



9. Mount in balsam. 



13. Pal's Modification of Weigert's Stain for the Medullary Sheath 

 of Nerves. This method is useful for the study of the central ner- 

 vous system, and may, with advantage, be preceded by staining 

 with neutral carmine. The tissues should have been fixed in a 

 chromate solution ; e. g., Miiller's fluid. 



1. Soak sections several hours in 1 per cent, chromic acid solu- 

 tion in water. 



2. Stain twenty- four to forty-eight hours in : 



Hematoxylin crystals, 1 gram, 



Absolute alcohol, 10 cc. 



Lithium carbonate (saturated aqueous solution), 7 " 

 Distilled water, 90 " 



The hymatoxylin crystals may be dissolved in the alcohol and 

 the solution kept in stock, the proper proportions of lithium carbon- 

 ate solution and water being added at the time of use. 



3. Wash in water to which a little lithium carbonate solution has 

 been added (about 2 cc. to each 100 cc. of water). The sections 

 should acquire a deep-blue color. 



4. Diiferentiate in 0.25 per cent, solution of potassium perman- 

 ganate in distilled water, till the gray matter e. </., of the spinal 

 cord becomes brownish-yellow (one-half to five minutes). 



5. Decolorize the gray matter in the following solution : 



Oxalic acid, 1 gram, 



Potassium sulphite, 1 " 



Distilled water, 200 cc. 



6. Wash thoroughly in distilled water. 



7. Dehydrate in 95 per cent, alcohol. 



8. Clear in carbol-xylol, oil of bergamot, or oil of origanum. 



9. Mount in xylol-balsam or xylol-dammar. 



This method stains the myelin-sheaths of the medullated nerve- 



