NEUROFIBRILS 485 



be " cleared " before dehydration in \ per cent, potassium ferri- 

 cyanide, followed by a wash in distilled water, and the usual 

 treatment with sodium hyposulphite. The method can be used 

 also for the study of the cerebral cortex where the fine (non- 

 medullated) fibres of the grey layers are well impregnated. If it 

 is desired to bring into \aew the axons of the large medullated 

 fibres the sections can, after cutting, be placed for six hours in 

 96 per cent, alcohol or in a bath consisting of 4 grm. of iron alum, 

 100 c.c. of distilled water and 1 grm. of oxalic acid. A similar 

 result can be obtained by adding to the silver-pyridin bath a 

 quarter its volume of 96 per cent, alcohol. 



1015. (2) Method for Central and Peripheral Nerve-endings 

 {Trab. Lab. Invest. Biol., xxiii, 1925 — 6, p. 237). Frozen sections 

 (30 — 40 fi) from formalin material are collected in distilled water, 

 washed and transferred for four to six hours into an impregnating 

 bath consisting of 2 per cent, silver nitrate 10 c.c, pyridin 7 to 

 10 drops, 96 per cent, alcohol 5 to 6 c.c. They should assume 

 a light brown colour, which can be intensified by placing the dish 

 over a flame for a few minutes. The sections are then quickly 

 washed (no more than two or three at a time) in 96 to 98 per 

 cent, alcohol, and immediately afterwards reduced in a bath 

 consisting of 0-30 grm. of hydroquinone, 70 c.c. of distilled water, 

 20 c.c. of formalin, 15 c.c. of acetone. After a few minutes they 

 are washed, toned, fixed and mounted in the usual way. 



1016. (3) Method for Pericellular Baskets, Moss and Climbing 

 Fibres {ibid., p. 240). This method can be considered as a simpli- 

 fication of the previous one. Frozen sections from formalin 

 material are impregnated and reduced at the same time in a 

 bath consisting of 10 c.c. of 2 per cent, silver nitrate, 10 drops of 

 pyridin and 7 to 10 drops of formalin. The sections become 

 dark brown in about four to six hours, when they are washed, 

 toned, etc., as above. This method is not recommended either 

 for the man or rabbit. 



De Castro's Modifications. The following formulae have recently 

 been suggested by De Castro {Trav. Lab. Rech. Biol., xxiii, 

 1925 — 6, p. 427) for fixing and decalcifying at the same time. 

 Small pieces can be fixed by means of one or the other of the 

 following mixtures. 



