84 Neurological Technique 



Warm the mixture, set aside to settle, and decant after cooling. Then 

 to each loo cc. of the methyl violet solution add 5 cc. of a 5 per cent, 

 aqueous solution of oxalic acid. 



F. Physiological salt solution (0.75 per cent. NaCl.). — r 



Sodium chloride, C. P., 1.5 g. 

 Distilled water, 200 cc. 



G. Lugol's solution. — 



Potassium iodide, 6 g. 

 Distilled water, 100 cc. 

 Iodine, 4 g. 



H. Differentiating fluid. 



Aniline oil (pure), 50 cc. 

 Xylol (pure), 50 cc. 



PROCEDURE. 



1. To yf;t;.— Place pieces of spinal cord or cerebral cortex 

 (human preferred) in 30-40 volumes of 10 per cent formalin (A) 

 in a tightly closing vessel, and let remain for 4 days or more. 



In the formalin, the tissues may be preserved for years with- 

 out disadvantage. 



2. From the formalin solutipn remove such pieces as are 

 desired (not thicker than 5 mm.) , and, without washing, place 

 them in 15-20 volumes of the chrom-alum solution (B). Place 

 the vessel in an incubator or thermostat and keep at a tempera- 

 ture of 38° C. for 6-8 days. 



The chrom-alum solution must be changed after the first and 

 third days, and better once or twice more during the period of 

 its action. 



3. Wash in 2 or 3 changes of distilled water for 10-15 

 minutes. 



The pieces are now a light greenish gray in color. 



4. Dehydrate with graded alcohols, imbed in celloidin, and sec- 

 tion, as in X, 3, 4, and 5, p. 64. 



Make sections of varying thicknesses. For general purposes 

 20 /A is recommended, but often thinner sections are better. 



5. Pass sections through decreasing grades of alcohol down to 

 water (X, 6), and from water transfer to the potassium permanga- 

 nate solution (C) for 10 minutes. 



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