4\'2 SPECIAL MICROSCOPIC TECHNIQUE. 



M filler's fluid is the most generally useful. Relatively large 

 quantities of this must be used. Marina's fluid consists of 100 

 cc. of 90 per cent, alcohol, 5 cc. of 40 per cent, forraol, and 10 

 grammes of chromic acid. Tissues hardened in this fluid may 

 be used for Weigert's or Nissl's method. Osmic acid, Flem- 

 ming's fluid, and absolute alcohol are used also for nervous 

 tissues. 



57. Staining of medullated fibres according to the Pal- 

 Weigert method is as follows : Tissue fixed in Muller's fluid is 

 transferred without washing in water to alcohol, in which it is 

 hardened in the dark. Celloidin sections (40-50 u) are cut, 

 and if not brown are allowed to stand for a few hours in 

 M Ciller's fluid. They are then stained for from twenty-four to 

 forty-eight hours in the following solution : hasmatoxylin, 1 

 gramme ; absolute alcohol, 10 cc. ; distilled water, 90 cc. ; sat- 

 urated aqueous solution of lithium carbonate, Ice. From this 

 the sections are transferred to a 13 per cent, solution of lith- 

 ium carbonate. When they are decolorized (after about one-half 

 hour) they are placed for one-half to one minute in a freshly 

 prepared 0.25 per cent, solution of potassium permanganate. 

 The sections are now washed in distilled water and placed in the 

 differentiating fluid, which consists of equal parts of 1 per cent, 

 solution of potassium sulphite and 1 per cent, oxalic acid. The 

 differentiation often takes an hour or more. The medullary 

 sheaths are colored dark blue, while the gray substance is 

 almost colorless. The sections should now be washed in 

 water, dehydrated, and mounted in balsam. They may be 

 counterstained in carmine, eosin, etc. 



58. Golgi's methods are uncertain, and are liable to produce 

 artifacts ; but a successful impregnation gives a specimen of 

 great value. The so-called rapid method is as follows : Small 

 pieces, 3-4 mm. thick, are immersed in a mixture of 1 volume 

 of 1 per cent, osmic acid, and 4 volumes of 3.5 per cent, potas- 

 sium bichromate solution. About 10 cc. of this mixture are 

 used for each piece of tissue. Hardening should take place in 

 the dark and at a temperature of 25 C. The time required 

 differs with the tissue used (e. g., two to three days with 



