430 CHAPTER XXXIV. 



quickly through the lower grades of alcohol, and not remain 

 for more than a few hours in alcohol of 95 per cent, or 

 absolute. They should be cleared with cedar oil (xylol 

 attacks the impregnation), and put direct into paraffin of 

 as low a melting point as possible. The cedar oil should 

 be used over and over again, as it takes up a little silver 

 (see BROOKOVER, Journ. Comp. Neurol., xx, 1910, p. 49). 



822. Mounting.- -Without special precautions, the stain will 

 not keep in sections mounted under a cover in the usual way. 

 An elaborate discussion (for which see previous editions] 

 between SEHRWALD (Zeit. wiss. Mik., vi, 1890, p. 443), 

 SAMASSA (ibid., vii, 1890, p. 26), and FICK (ibid., viii, 1891, 

 p. 168) furnishes the net practical result that watery fluids 

 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, for study, inverted 

 over the aperture of a hollowed-out wooden slide ; or that 

 the balsam of the mount shouldbe 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. 

 An?.., vii, 1892, p. 587). I think it is safer to keep the 

 mount uncovered till the sections have become quite dry in 

 it, and the balsam (applied from time to time in thin layers) 

 quite hard; then cover with a warmed cover pressed down. 



But if mounting under a cover at once be preferred, one 

 of the following methods may be employed. 



823. GREPPIN'S Process (Arch. Anat. Entw. Anat. Abth., 1889, 

 Supp., p. 55). Sections are treated for thirty to forty seconds (until 

 whitish) with 10 per cent, solution of hydrobromic acid, and then well 

 washed in several changes of water and mounted under a cover in the 

 usual way. They can be further reduced in sunlight if desired. Further 

 details in previous editions. 



824. OBREGIA'S Process (Virchow's Archtv, cxxii, 1890, p. 387).- 

 Sections 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 



