NEUROFIBRILS 495 



night). They are rinsed quickly in absolute alcohol and reduced in 

 pyrogallic acid, 5 grm. ; neutral formalin, 5 e.c. ; 95 per cent, alcohol, 

 100 c.c. ; 50 per cent, commercial dextrin, 5 drops. Development 

 usually takes about two minutes, and if the developer be kept turbid 

 by the addition of a few drops of the dextrin from time to time many 

 sections can be reduced without renewal of the developer. The slides 

 are then passed through two or three changes of 95 per cent, alcohol, 

 absolute alcohol and ether, xylol and mounted in balsam. Clearing of 

 the background may be effected with acid sodium hyposulphite, and if 

 desired, sections may be toned with gold chloride. 



Kernohan {Trans. Am. Micros. Soc, xlix, 1930, p. 58) cuts frozen, 

 parafhn or celloidin sections at 6-15 fi, and after washing thoroughly 

 in distilled water immerses them for an hour in 20 per cent, silver 

 nitrate. The sections are washed quickly twice and transferred to a 

 solution prepared by adding ammonia drop by drop to 10 c.c. of 20 per 

 cent, silver nitrate until the precipitate is almost dissolved. Excess of 

 ammonia is to be avoided and the solution is filtered before use. Sec- 

 tions stay in the silver bath from one to four minutes and are washed 

 rapidly before reduction in 10 per cent, neutral formalin. It is often 

 advisable to remove celloidin from celloidin imbedded material before 

 impregnating with silver. 



Trelles {Rev. Neurol., i, 1932, p. 459) uses a similar method with 

 celloidin sections ; and Reumont {Rev. Neurol., ii, 1931, p. 53) stains 

 frozen sections similarly after a bath of nicotinised alcohol. 



See also Schultze and Stohr {Anat. Anzeiger, liv, 1921, p. 529) and 

 LouGHLiN (Arch. Neurol, and Psychiat., xxxiii, 1935, p. 616). 



The methylen blue intra-vitam method is important, and may 

 be usefully employed for the study of neurofibrils. See the 

 processes of Apathy, Dogiel, and Bethe in Chapter XVI. 



