32 Neurological Technique 



E. Mounting medium (glycerine jelly), Kaiser's formula. — 



Finest French gelatin, 5 g. 

 Distilled water, 30 cc. 



Put the gelatin in the water and set aside for two hours or more in a cov- 

 ered vessel. 



Then add pure glycerine, 35 cc. 



and pure carbolic acid, 0.5 g. 



Warm the mixture (about 70 C.) for 1 5-20 minutes and stir till the whitish 

 flakes produced by the carbolic acid have all disappeared. Then, while 

 warm, filter carefully. Fine-spun glass, wet in warm water and placed in the 

 neck of the funnel, may be used for filtering. The carbolic acid is added as 

 a preservative. An equal amount of thymol may be used instead. In mount- 

 ing, the glycerine jelly must first be warmed till melted, then it may be used 

 after the manner of balsam (I, 16, p. 19). 



PROCEDURE. 



1. To fix, place sections of fresh spinal cord, 2—4 milli- 

 meters thick, or small pieces of tissue such as ganglia, 

 or pieces of tissue containing sense organs, in 20—30 times 

 their volume of the osmic acid-sublimate solution (A) for 24 

 hours. This, and the succeeding process up to the point of 

 imbedding in paraffin, is carried on in the dark. A cool 

 thermostat or specially prepared dark-box may be used. A 

 good dark-box may be made of an ordinary tight wooden box 

 with a closely fitting hinged cover or door. The inside of the 

 box should be painted black. 



2. To wash, remove the tissue from the fixing fluid, rinse 

 well with distilled water, and transfer to 15-20 volumes of the 

 iodine solution (B) for 10-12 hours. 



If, during the washing period, the fluid becomes decolorized, 

 renew it. 



The iodine solution, by forming the more soluble iodide, frees 

 the tissue of products which otherwise cause crystals in the prep- 

 arations, brittleness, and imperfect staining. 



The time necessary for washing may be very much reduced 

 by treating the sections on the slide with the iodine solution 

 instead of the tissue in bulk, but neglect to wash out before the 

 process of imbedding sometimes gives rise to serious artefacts. 



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