54 , Neurological Technique 



gold chloride solution for 15-20 minutes. Here they become 

 yellow and slightly shrunken. They are then placed in the 

 2 per cent, formic acid solution (D) for reduction, and further 

 treated as in 4, 5, and 6 



While the use of formic acid as the first fluid seldom fails to 

 give stained nerve terminations, the action of the acid causes 

 the tissue elements to swell and become much distorted. When 

 first fixed and preserved in formalin, the tissues pass through the 

 formic acid unaltered, and consequently preparations made from 

 formalin material are more nearly normal and trustworthy in their 

 appearances. Again, if it is desired to imbed the material swollen 

 by the action of formic acid, the action of the alcohol in dehy- 

 dration produces a violent shrinkage which tends to increase the 

 defects of the preparations. For these reasons formalin material 

 is recommended, though its use may result in more frequent 

 failures to get well-stained nerve terminations. 



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