CHAPTER XXXIV. 469 



method, or the like, is particularly desirable. Tn this case one of the 

 following methods may be employed : 



GKEPPIN (Arch. Anat. u. Entwick., Anat. Abth., Supp., 1889, p. 55) 

 treats sections for thirty to forty seconds (until whitish) with 10 per 

 cent, hydrobromic acid, washes them in several changes of water, 

 dehydrates, clears with clove oil and exposes them for ten to fifteen 

 minutes to sunlight. 



OBREGIA (Virchow's Arch., cxxii, 1890, p. 387) transfers sections into 

 a mixture of absolute alcohol, 10 c.c., and 1 per cent, gold chloride, 

 10 drops, to be previously exposed to diffuse daylight for half an hour. 

 Sections are then passed into it and put in a dark place. After fifteen 

 to thirty minutes they are washed successively in 50 per cent, alcohol, 

 distilled water, 10 per cent, sodium hyposulphite (five to ten minutes), 

 and repeatedly changed distilled water. They may be then counter- 

 stained, dehydrated and mounted in balsam under a cover. 



KALLIUS (Anat. Hefte., ii, 1893, p. 271) uses 230 c.c. of distilled 

 water and 20 c.c. of commercial hydro quinone solution (hydroquinone 

 5 grms., sodium sulphite 40 grms., potassium carbonate 75 grms., dis- 

 tilled water 250 c.c.). The solution is further diluted before using with 

 one-third to one-half its volume of absolute alcohol and the sections 

 (freed from unreduced silver by washing them in many changes of 

 alcohol) left in it for several minutes. Here they become dark-grey to 

 black, and are then transferred for ten to fifteen minutes into .70 per 

 cent, alcohol, for five minutes into 20 per cent, sodium hyposulphite, and 

 for twenty-four hours into a large quantity of distilled water. Counter- 

 stain, dehydrate, clear and mount as usual. 



EBERTH and RUNGE (Arch. mikr. Anat., xlvi, 1896, p. 370) have 

 successfully used a process similar to that of Greppin. They convert 

 the silver impregnation into silver chloride by keeping sections in 

 chlorine water for fifteen to twenty minutes, and they then reduce the 

 white silver chloride, either through exhibition to sunlight just before 

 mounting, or by means of Kallius' process. 



BOLTON (op. cit.) has obtained good results with Kallius' process 

 applied to his f or mol- bichromate modification. 



CUKRERI (Anat. Anz., xxxii, 1908, p. 432), after fixing by Kallius' 

 method, tones in 0-7 grm. of gold chloride, 3 grm. of sodium acetate 

 and 100 c.c. of water. 



ZIMMERMANN'S process (Arch. mikr. Anat., Hi, 1898, p. 554). Paraffin 

 sections of formol-Golgi material are brought from alcohol into a large 

 quantity of a mixture of 1 part of physiological salt solution and 2 parts 

 of 96 per cent, alcohol. They are kept in motion therein for ten to fifteen 

 minutes, after which they are brought into 75 to 96 per cent, alcohol 

 in a bright light until they have become dark (about half a day) ; or 

 sections are left for half to one hour in 100 c.c. of absolute alcohol to 

 which a few drops of ammonium hydrosulphide have been added. In 

 the first case the silver deposit becomes converted into silver chloride, 

 in the second into silver sulphide. Later (Arch. mikr. Anat., Ixxviii, 

 1911, p. 199) he reduces for several hours in 20 c.c. of saturated 

 solution of sodium carbonate (made up with 50 per cent, alcohol) to 

 which 0-5 grm. of adurol are added. These processes are useful for 



