486 NEUROFIBRILS 



3. Somnifene (Hoffmann — La Roche) . 2 to 4 c.c. 



Alcohol (presumably 96 per cent.) . 60 c.c. 



Distilled water . . . . 40 ,, 



Nitric acid 3 to 4 c.c. 



After one to three days decalcification is complete, particularly 

 if the pieces are small and from very young or foetal mammals. 

 They are washed in distilled water for twenty-four to thirty-six 

 hours to extract the nitric acid and then transferred into alcohol, 

 96 per cent, containing 4 to 6 drops of ammonia for every 50 c.c. 

 of alcohol. After twenty-four hours they are silvered and reduced 

 as by Cajal's method. Some pieces can, after washing, be dehy- 

 drated and imbedded either in celloidin or paraffin and the 

 sections stained by either the Nissl method or ordinary methods. 



1017. Bielschowsky's Methods. Introductory. It is well 

 known that, if ammonia be poured into a solution of silver 

 nitrate, a precipitate is formed which is re-dissolved by the 

 addition of some more ammonia. If an alkaline solution of 

 formaldehyde be slowly added to this easily reducible diam- 

 moniacal silver nitrate (N(NH4)AgH2NO;.), metallic silver is 

 immediately precipitated and deposited on the walls of the 

 test-tube. Both Fajerstajn {Neurol. Centrbl., xx, 1901, p. 98) 

 and BiELSCHowsKY {ibid., xxi, 1902, p. 579) 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 superseded ; Bielschowsky also published, at first, a complicated 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 Da Fano 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 Da Fano 

 gained through a visit paid to him when in Berlin. 



1018. Bielschowsky's Method for Sections {Journ. Psychol. 

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



