CHAPTER IX 



METALLIC SUBSTANCES FOR COLOR DIFFERENTIATION 

 I. A GOLGI METHOD FOR NERVE CELLS AND THEIR RAMIFICATIONS 



The Golgi chrom-silver method is one widely used for the 

 demonstration of nerve cells together with their various processes. 

 There are many modifications of the method all of which are more 

 or less inconstant in their results. In a successful preparation, 

 the various cells and nerve processes are not equally blackened, a 

 fact which allows of discrimination between the different elements. 

 Sometimes the ganglion cells and fibers remain unstained while 

 the neuroglia cells are impregnated, or occasionally other elements 

 than nervous tissue (e. g., blood-vessels) are affected. 



The following method is applied to material preserved in 10 

 per cent, formalin and is a so-called "rapid method." 



1. From the brain and spinal cord which have previously (see 

 note, p. 38) been subdivided and placed in at least 10 times their 

 volume of 10 per cent, formalin (3 days to an indefinite time), 

 cut out small pieces 4 to 5 mm. thick from the region desired for 

 study and transfer them to a vessel containing from 15 to 20 times 

 their volume of a 3.5 per cent, aqueous solution of potassium 

 bichromate. They should remain in this solution for from 2 to 5 

 days. Renew the fluid at the end of 12 hours. Keep the different 

 pieces of tissue in separate vessels so as to avoid confusion. 



2. For impregnation, transfer the tissues to a silver nitrate 

 solution made as follows: 



Silver nitrate (crystals) 1.5 grams 



Distilled water 200.0 c.c. 



Concentrated formic acid 1.0 drop 



3. Rock the tissues gently in a small amount of this fluid until 

 the brown precipitate of silver chromate ceases to appear, then 

 transfer them into from 20 to 40 times their bulk of fresh silver 

 nitrate solution and leave them in the dark for from 3 to 6 days. 

 Change the fluid after the first 12 hours. 



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