GOLGl's BICHROMATE OF SILVER METHOD. 371 



3. Dehydrate small pieces with, alcohol (make sections if 

 necessary), clear in oil of turpentine, tease in the turpentine, 

 and mount in dammar. 



4. The preparations are then left to themselves in order 

 that the secondary impregnation may take place. In direct 

 sunlight eight to ten days will complete the process; in 

 diffused daylight (or in the dark ?), twenty, thirty, or forty 

 days. 



A somewhat greater precision of the reaction is obtained by treating the 

 fresh tissues with osmic acid (by means of insterstitial injection) before 

 putting them into the bichromate. In this case a much shorter immersion 

 in the bichromate will suffice (four, six, or eight days). 



By this means may be demonstrated in the medullated fibres of the spinal 

 cord a chain of conical funnels, set one within another, and embracing the 

 axis-cylinder with their narrow aperture, and the external surface of the 

 following funnel with their greater aperture ; and it is seen that they con- 

 sist of a fine spiral fibre wound into the form of a funnel. (The appear- 

 ance of rings and strainers is due to imperfect action of the silver.) 



705. For the Study of Peripheral Nerves Golgi modifies the 

 process as follows (1. c., 1879, p. 238) : 



1. Pieces of nerve are immersed in the bichromate solution, 

 for from four, six, or eight hours to one day, or at most two 

 days. 



2. From time to time pieces are removed into the nitrate 

 of silver; they remain there for from twelve to twenty-four 

 hours. 



3. They are washed with several changes of alcohol. 



4. Tease in the alcohol, dehydrate, clear with turpentine, 

 mount in dammar. 



5. Reduce in direct sunlight ; in summer a few days suffice, 

 in cold weather some weeks are necessary. 



Does not give quite such fine results as the osmium bichro- 

 mate and silver method, or "rapid" method, next to be 

 described ; but the preparations keep indefinitely. 



706. The Osmium, Bichromate, and Silver Method, or Rapid 

 Method (ibid., p. 237). A perfectly fresh piece of nerve is 

 thrown into the following liquid : 



2 per cent, solution of bichromate of 



potash 10 parts. 



1 per cent, solution of osmic acid . 2 

 After about an hour's immersion the piece of nerve may 



