NEUROLOGICAL METHODS. 423 



should be avoided as much as possible during the after- 

 treatment, and that sections should either be mounted with- 

 out a cover, or on a cover raised free of contact with the 

 slide by means of wax feet or the like ; or that the balsam 

 of the mount should be rendered perfectly anhydrous by 

 careful heating on the slide, with the section in it, until it 

 immediately sets hard on cooling, before the cover is 

 applied. 



This last method is also recommended by HUBER (Anat. 

 Am., vii, 1892, p. 587; Journ. Roy. Hie. Soc., 1892, p. 707; 

 Zeit. f. wiss. Mik., ix, 4, 1893, p. 479) . 



The majority of workers seem to abide by this result, and 

 to consider that the fixation methods shortly given in the 

 next four sections are, to say the least, superfluous. 



759. GEEPPIN'S Process (Arch. f. Anat. u. Entw., Anat. Abth., 1889, 

 Supp., p. 55 ; Zeit. f. wiss. Mik., vii, 1, 1890, p. 66). After silvering, 

 sections are made with a freezing microtome and treated for thirty to 

 forty seconds with 10 per cent, solution of hydrobromic acid, and may then 

 be well washed in several changes of water and mounted under a cover in 

 the usual way. Further details in previous editions. 



760. OBBEGIA'S Process (Virchow's Archiv, cxxii, 1890, p. 387; Zeit. 

 f. wiss. Mik., viii, 1, 1891, p. 97 ; Journ. Boy. Mic. Soc., 1891, pp. 536, 



830; Amer. Mon. Micr. Journ., 1891, p. 210). Sections of silvered 

 material are made, either without imbedding, or after imbedding either in 

 paraffin or celloidin, care being taken in either case not to use alcohol of a 

 lower grade than 94 or 95 per cent. They are brought from absolute 

 alcohol into a mixture of eight to ten drops of 1 per cent, solution of gold 

 chloride with 10 c.c. of absolute alcohol, which should be prepared half an 

 hour beforehand and exposed to diffused light until the sections are placed 

 in it, when it should be put into the dark. After fifteen to thirty minutes 

 therein, according to their thickness, the sections are quickly washed in 50 

 per cent, alcohol, then in water, then treated for five or ten minutes with 

 10 per cent, solution of hyposulphite of soda. They are lastly washed well 

 with water, and may then be mounted at once in balsam under a cover, or 

 if desired may be previously stained with carmine or haernatoxylin, or Pal's 

 modification of Weigert's process, or the like. 



761. KALLIUS (Anat. Hefte, ii, 1892, p. 269 ; Zeit. f. wiss. Mik., ix, 4, 

 1893, p. 477) has worked out the following process. Take 20 c.c. commercial 

 hydroquiuone developing solution and 230 c.c. distilled water (the hydro- 

 quinone solution may be made up with 5 grins, hydroquinone, 40 grms. 

 sodium sulphite, 75 grms. carbonate of potassium, and 250 grms. distilled 

 water). At the instant of using, further dilute the solution with one third 



