CHAPTER XXXV. 481 



article " Neurogliafdrbung " in EnzyU. mik. 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 

 2J per cent, of chrome alum, in water. (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 solution, so that the hardening and 

 mordanting are done at the same time. 



After mordanting, the tissues are washed, dehydrated, embedded 

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

 ten minutes with a ^ 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 manufactory. 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. They are then differentiated till clear 

 and light blue with a mixture of equal parts of aniline oil and xylol, 

 washed thoroughly with pure xylol, and mounted in balsam or, 

 preferably, in turpentine-colophonium. 



Glia fibres and nuclei blue, cytoplasm stainless. 



This method only gives good results with the human subject. 



911. Modifications of WEIGERT'S Method. MALLORY (Journ. Exper. 

 . y 1897, p. 532) fixes tissues for four days in 10 per cent, solution of 



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