458 AXIS-CYLINDER AND DENDRITE STAINS. 



wish, either on ordinary slides, or on coverslips if the Golgi hollowed- 

 out wooden slides are preferred for definite preservation. The 

 excess of cedar-wood oil carried with the spatula is removed by 

 covering the sections, after having definitely arranged them on the 

 slides, first with a sheath of cigarette paper and then with a folded 

 piece of filter paper, to be held by the left hand while the right is 

 passed over it so as to press down the sections and absorb the oil. 

 The whole manoeuvre may be repeated a second time, and then a 

 drop of thick cedar-wood oil put on each section. On the next 

 day the oil which may have run from the sections is cleaned from 

 the edges of the slides and a fresh drop of the thick cedar-wood oil 

 put on the sections, to be protected from dust and light at least 

 until the oil has become quite dry. 



Preparations mounted in this way last for years unaltered ; in 

 fact, I have some which were made in Golgi's laboratory over 

 fifteen years ago and I find that they have kept without change. 



1 have no experience of the use of creosote or of the mixture, 

 originally proposed by Andriezen, of equal parts of pyridine and 

 xylol instead of the guaiacol, but they should equally well serve 

 the purpose. 



As a general rule one makes sections of 20 to 40 //, ; thicker sections 

 of 50 to 60 ju, or more, show more than thin ones but do not seem to 

 keep so well. 



The order in which the elements of nervous tissues impregnate 

 is generally first, axis-cylinders, then nerve cells, and lastly, 

 neuroglia cells. 



882. GOLGI'S Bichromate and Nitrate of Silver Method. KAPID 



PROCESS. Small pieces of very fresh tissues are hardened in a mixture 

 of 2 to 2-5 per cent, potassium bichromate 8 parts, and 1 per cent, 

 osmic acid 2 parts. Or, if a very quick hardening is desirable, 



2 parts of 3 per cent, bichromate to one of 1 per cent, osmic acid. 

 In Golgi's laboratory mixtures of 3 parts of 3 per cent, bichromate 

 and 1 of 1 per cent, osmic acid are now generally used. The tissues 

 begin to be in a state suitable for the silver impregnation from the 

 second or third day ; in the next following days they are in a still 

 more favourable state, but this soon declines, and is generally quite 

 lost by the tenth or twelfth day. 



The silver impregnation is conducted exactly in the same way as 

 in the slow process, and sections are prepared and mounted in the 

 same manner, but they should not be left in alcohol for more than 

 an hour or so before mounting. 



