34 HISTOLOGICAL TECHNIC 



Sections from material fixed in any of the chrome-salt solutions 

 are placed for from twelve to twenty-four hours in a saturated aque- 

 ous solution of neutral cupric acetate diluted with an equal volume of 

 water. The cupric acetate forms some combination with the tissues 

 which intensifies their staining qualities, thus acting like the chrome 

 salts as a mordant. 



After mordanting, the sections are washed in water and trans- 

 ferred to the following staining fluid: 



Haematoxylin crystals, i gm. 



Alcohol, 95-per-cent., 10 c.c. 



Lithium carbonate — saturated aqueous solution, i c.c. 



Water, 90 c.c. 



This solution must either be freshly made before using, the haema- 

 toxyhn being dissolved first in the alcohol, or the haematoxyhn may 

 be kept in lo-per-cent. alcohohc solution, the hthium carbonate in 

 saturated aqueous solution, and the staining fluid made from these 

 as needed. 



Sections remain in the haematoxylin solution from two to twenty- 

 four hours, the longer time being required for staining the finer fibres 

 of the cerebral and cerebellar cortices. They are then washed in 

 water and decolorized in the following: 



Potassium ferricyanid, 2.5 gm. 



Sodium biborate, 2.0 gm. 



Water, 300.0 c.c. 



While in the decolorizer, sections should be gently shaken or moved 

 about with a glass rod to insure equal decolorization. In the decolor- 

 izer the sections lose the uniform black which they had on removal 

 from the haematoxyhn. They remain in the decolorizing fluid until 

 the gray matter becomes a Hght gray or yellow color, in sharp con- 

 trast with the white matter which remains dark. Sections are then 

 washed in several waters to remove all traces of decolorizer, and de- 

 hydrated in alcohol. 



Weigert-Pal Method. — In this modification of the Weigert 

 method, material hardened in formalin should be further hardened in 

 potassium bichromate 5-per-cent. for two weeks, or in copper bichro- 

 mate 3-per-cent. for about a week, after which it may be cut and 

 stained without further mordanting. Sections from material hard- 

 ened in the other above-mentioned ways are mordanted in a 3- to 5- 

 per-cent. aqueous solution of potassium bichromate instead of in the 



