METHODS OF STAINING. 311 



fluid, or sublimate solution. The connective-tissue fibres are stained 

 red bv the acid fuchsin. The reason for overstaining with hsema- 

 toxylin is that subsequent treatment with picric acid discharges 

 some of that color. 



12. Benda's Iron-haematoxylin Stain. — This is a powerful stain 

 well adapted to the staining of paraffin-sections that have been 

 affixed to cover-glasses. It stains nuclei and intercellular sub- 

 stances, as well as the protoplasm of cells, various shades of gray, 

 and the color is very permanent. The outline of the method is as 

 follows : 



1. Mordant the sections (after affixing to cover-glasses, if that 

 method is used) in a mixture of equal parts of liquor ferri sul- 

 furici oxydati of the German Pharmacopoeia and distilled water for 

 twenty-four hours. 



2. Rinse in distilled water, and then wash in three changes of 

 tap-water. 



3. Stain in aqueous solution of hematoxylin, prepared by mix- 

 ing 10 drops of a concentrated alcoholic solution of the crystals 

 with 10 cc. of distilled water. Stain for from one-half to twenty- 

 four hours. 



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., Muller'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 " 



