158 A REVIEW OF THE GOLGI METHOD. 



changes of the results which it yields and the treatment which it 

 requires are to be ascribed to the newly-added reagent, partly 

 because the process so modified can remedy some inconveniences 

 of the original method. 



" It can be applied in two ways, namely : — 



" (a) By laying small pieces of nervous tissue directly in a 

 mixture of bichromate and osmic acid (2 per cent, to 2J per cent, 

 solution of bichromate, 8 parts ; i per cent, solution of osmic 

 acid, 2 parts). 



" The black stain is obtained the most quickly with this pro- 

 cedure. The black staining of a great number of nervous elements 

 can be obtained by transferring into silver at the second or third 

 day (see the directions for procedure in the description of the 

 original method). The reaction extends itself on the immediately 

 following days, then, as usual, diminishes, and at the tenth or 

 twelfth day entirely ceases. 



" The treatment of the macro- and micro-scopical preparations 

 which are obtained in this way must be considerably modified. 

 Pieces prepared by this method differ from those prepared by the 

 first method inasmuch as when they are kept a long time, for 

 future use, they become diffusely blackened, and thereby useless. 

 They must be kept in the same silver solution which has served for 

 the reaction. Then they are brought into pure alcohol, which must 

 be changed, where they remain not longer than two days, sectioned 

 and subjected to the above described treatment (absolute alcohol 

 with repeated washing, creosote^ turpentine, damar) necessary for 

 their permanent preservation as microscopical preparations. 



" Although this application of the osmium-bichromate solution 

 is certain, and, as far as fineness is concerned, yields satisfactory 

 results, yet I find that, for a systematic study of any definite portion 

 of the nervous system, the following method is far preferable : 



" (^) Bringing of fresh pieces into the bichromate solution ; first 

 transference into an osmium-bichromate solution ; second transference 

 into the silver solution. It is different with this second procedure 

 than with the preceding, in which the series of pieces of tissue to 

 be examined are useless after a few days. Here the fresh pieces 

 (with or without injection) are laid in the bichromate solution, and 

 remain, so to speak, in the hand of the investigator. They can 



