CHAPTER XXXII. 427 



thought of taking advantage of this reaction for histological purposes 

 with the object of finding out a silver impregnation of the nervous 

 tissue similar to that which characterises Golgi's method. The 

 results of their attempts were different : Fajerstajn was able to 

 obtain only a difficult method for staining axis-cylinders which 

 is now superseded ; Bielschowsky also published, at first, a 

 complicated silver method for impregnating axis-cylinders very 

 similar to that of Fajerstajn, but, through successive modifications 

 of his first process, was led to the discovery of a new method, which 

 is as important as Cajal's reduced silver methods from an histological 

 point of view, but is of still greater advantage than the latter for 

 histopathological investigations. Moreover, Bielschowsky's method 

 is applicable to any formol material, even if very old. BAYON 

 (Die Untersuchungsmeth, etc.) succeeded with four-year-old material, 

 and I with brains which had been left in formalin for more than 

 eleven years. 



There are at present three Bielschowsky methods : one for sections, 

 one for peripheral nerve-fibres and axis-cylinders, and one for pieces. 

 It seems better to describe them separately in the following account 

 which is based on the original papers of Bielschowsky, as well as 

 on some personal experience I gained through a visit paid to him 

 when in Berlin. 



BIELSCHOWSKY'S Method for Sections (Journ. Psychol. NeuroL, 

 iii, 1904, p. 169 ; and xii, 1909, p. 135). Pieces from central nervous 

 organs, fixed in 15 to 20 per cent, formalin, are washed for some 

 hours in running tap-water and then cut by means of a C0 2 freezing 

 microtome. The sections are collected in distilled water, thoroughly 

 washed therein and passed in a 2 or 3 per cent, solution of silver 

 nitrate where they are left for twenty-four hours in a dark place, 

 and at room temperature. The sections can also be passed first 

 into pure pyridine for twenty -four to forty -eight hours, washed in 

 many changes of distilled water until the pyridine has been completely 

 eliminated and then transferred into 2 to 3 per cent, silver nitrate 

 as above. 



The pyridine bath is optional and has the advantage of ensuring a 

 sharper stain of axis-cylinders whilst neuroglia, which is more or 

 less coloured when the pyridine bath is dispensed with, remains 

 unstained. Also connective tissue and nuclei are generally very 

 faintly stained after the pyridine treatment. Intracellular neuro- 

 fibrils, however, are not always so well shown as by the direct passage 

 of sections into the silver nitrate solution. 



Before proceeding further, one should prepare the Bielschowsky 



