NERVOUS SYSTEM GENERAL METHODS. 377 



the chromic salts, and even than alcohol, and allows of the 

 most various xtains, including silver neuro-fibril stains and 

 the Golgi impregnation. 



Several writers insist that for nervous tissue it should not 

 le acid; but some prefer it acid (see " Retina"). For 

 neuro-fibrils it certainly should be neutral. To neutralise, 

 it is generally sufficient to make up the solutions with tap- 

 water. It is not likely to overharden. 



I use 1 part of formol to 9 of water (or 8 if the formol 

 has been keep long). 



WEIGERT (Beit. Kenidn. norm, mensch. Neiiroglia, 1895, 

 p. 1146) puts portions of material of not more than half a 

 centimetre in thickness for four days into a " 4 per cent, 

 solution of formol " (meaning, presumably, 4 per cent. 

 formaldehyde). 



MARCUS (quoted from FISH, see below) hardens spinal cord 

 for two or four weeks in a 4- per cent, solution of "formalin," 

 (meaning also probably formaldehyde), then in Miiller's fluid 

 for a week in an oven at 37 C. 



VAN GIBSON (Anat. Anz., x, 1895, p. 494) has used 

 " solutions of formalin of 4, 6, and 10 per cent.," followed 

 by 95 per cent, alcohol. Myelin was found to be well 

 preserved. 



LACHI (cf. Zeit. iviss. Mik., xii, 1895, p. 32) has had good 

 results with " 20 per cent, solutions of formol." 



FISH (Proc.Amer. Mic. Soc., xvii, 1895, p. 319) recommends: 



Water 2000 c.c. 



Commercial formalin ... 50 



Sodium chloride . . . .100 grms. 



Zinc chloride . . . . . 15 



Brains should be left in this mixture for a week or ten days 

 or more, then transferred to a solution of water 2000 c.c., 

 formalin 50 c.c., in which they may remain indefinitely if 

 the jar be kept tightly covered. 



PARKER and FLOYD (Anat. Anzeiyer, Bd. ix, 1895, p. 150) 

 advise (for sheep's brains) a mixture of 



Alcohol 95 per cent. . . .6 volumes 



Formol 2 per cent. . . 4 



Brains may be kept for months in the mixture (ibid.j 

 1806, p. 5G8). 



FLATAU (Anat. Anz., xiii, 1897, p. 323) finds that brain 



