502 GOLGI 



of greatly hastening the process whenever desired by simply 

 bringing all the pieces over at once into the osmic mixture. Lastly, 

 a still greater delicacy of results, particularly noticeable in the 

 staining of axons and their collaterals. 



1030. GoLGi's Methods for demonstrating Funnels and Spiral 

 Filaments. Golgi (see Rezzonico, Arch. p. I. Sc. Med., iv, 1880, 

 p. 78 ; Golgi, Opera Omnia, I, p. 163) puts small pieces of spinal 

 cord in 2 per cent, potassium bichromate for eight to fifteen days 

 in summer, or a month in winter. After a quick wash he transfers 

 them into 0-50 to 0-75 per cent, silver nitrate for two or three 

 days in summer, or eight, ten or more in winter. The pieces 

 are then washed in 95 per cent, alcohol, dehydrated in absolute 

 alcohol, cleared in oil of turpentine and teased therein. The 

 preparations, mounted in dammar, must be exposed to sunlight 

 for eight to ten days ; or to diffused daylight for twenty to forty 

 days. 



For Peripheral Nerve-fibres, Golgi (Op. Omnia, I, p. 162) has 

 proposed two methods. Of these the first is a modification of his 

 rapid process (see § 1028), and should be carried out as follows : — 

 Tracts of peripheral nerves are cut with care not to stretch them, 

 and put in a mixture of 10 parts of 2 per cent, potassium bi- 

 chromate and 2 of 1 per cent, osmic acid. After about one hour 

 the tract or tracts of nerves are sufficiently hardened to be further 

 recut in pieces of about | cm. in length, which are put back in the 

 same mixture. After another three hours, and successively at 

 intervals of three hours during twenty-four hours, pieces are 

 transferred into 0-5 per cent, silver nitrate where they may remain 

 for any time, but no less than eight hours. Preparations are 

 made and mounted as above. 



The other method is a modification of that used for central 

 nerve-fibres, the only difference consisting in keeping the pieces 

 in the bichromate for a much shorter period, i.e. for from four 

 hours to at most two days, and in transferring specimens into 

 the silver bath at intervals of about three hours. After twelve 

 to twenty-four hours preparations can be made as described above. 



The preparations made by the first method show the spiral 

 filaments very clearly, but do not keep well. The preparations 

 made by the second method do not show the spiral filaments so 

 completely, but are more useful for the demonstration of the 

 funnels and last longer. 



Cattani (Arch. Ital. Biol, vii, 1886, p. 345) either fixes in 

 Flemming's fluid and teases and mounts in glycerin, or puts 

 pieces into Golgi's bichromate and osmic acid mixture, dehydrates 

 and passes into oil of turpentine to be changed until it remains 

 colourless. The turpentine dissolves the myelin and leaves 

 funnels and spiral filaments visible. Cattani also has a modified 

 Golgi method, now superseded. 



