NEUROGLIA AND SENSE ORGANS 537 



bodies and processes of the fibrous, protoplasmic and interfascicular 

 glia, but not on the microglia. 



For minute technical details and some of the less commonly 

 used methods, the original papers quoted in the following para- 

 graphs should be consulted as well as NissL (Enzykl. viikr. Techn., 

 ii, 1910, pp. 280 to 283) ; Bonome {Atti R. Inst. Veneto Sc, Ixvii, 

 1909). 



METHODS FOR FIBROUS NEUROGLIA 



1083. Weigert's Neuroglia Stain (Weigert's Beitr. zur 

 Kenntniss d. norm, mensch. Neuroglia, Frankfurt-a.-Main, 1895 ; 

 and the article '''' Neurogliafarhung" in Enzykl. rnik. Technik. ii, 

 1910). Pieces of very fresh tissue of not more than ^ cm. in 

 thickness are put, for at least four days, into 10 per cent, formol. 

 They are then mordanted for four or five days at 36° to 37° C. 

 (or for at least eight days at the temperature of the laboratory) 

 in a solution containing 5 per cent, of neutral copper acetate, 

 5 per cent, of acetic acid, and ^\ per cent, of chrome alum, in 

 water. " Gliaheize." — (Add the alum to the water, raise to 

 boiling point, and add the acetic acid and the acetate, powdered, 

 or, instead of chrome alum, take chromium fluoride, which 

 obviates the necessity of boiling.) If preferred, the mordant may 

 be dissolved in the formol sohition, so that the hardening and 

 mordanting are done at the same time. 



After mordanting, the tissues are washed, dehydrated, im- 

 bedded in celloidin, and cut. The sections (not too thick) are 

 treated for ten minutes with a i per cent, solution of potassium 

 permanganate and well washed in water. They are then treated 

 for two to four hours with a solution of " chromogen." This is a 

 naphthaline compound prepared by the Hoechst dye manufac- 

 tory. The solution to be used is prepared as follows : 5 per cent, 

 of " chromogen " and 5 per cent, of formic acid {of 1-20 sp. gr., 

 about four times as strong as the officinal) are dissolved in water, 

 and the solution carefully filtered. To 90 c.c. of the filtrate, 10 c.c. 

 of a 10 per cent, solution of sodium sulphite are added. 



After this the sections are put till the next day into a saturated 

 (about 5 per cent.) solution of " chromogen." (According to 

 Bolles Lee, Pal's potassium sulphite may be used instead of the 

 " chromogen.") 



They are next carefully washed and stained. This is best 

 done on the slide. The stain is a warm-saturated solution of 

 methyl violet in 70 to 80 per cent, alcohol (to which, after cooling 

 and decanting, there may be added, if desired, 5 per cent, of a 

 5 per cent, aqueous solution of oxalic acid). The sections are 

 treated with this for from a few seconds to one minute, and 

 mopped up with blotting-paper, then treated for an instant 

 with saturated solution of iodine in 5 per cent, potassium iodide. 



