468 AXIS-CYLINDER AND DENDRITE STAINS. 



Embedding in paraffin is also possible, but results are usually 

 rather poor, and one should have recourse to it only for special 

 objects, such as muscles (see VEBATTI, Mem. R. Inst. Lomb. Sc., xix, 

 1902, p. 87). In any case tissues should be passed quickly through 

 the lower grades of alcohol, and remain only a few hours in 95 per 

 cent, and absolute alcohols. They should be cleared with cedar- 

 wood oil, as xylol and similar reagents may be injurious to the 

 silver impregnation. One should transfer pieces directly into 

 paraffin of as low a melting point as possible. According to 

 BROOKOVER (op. cit.), cedar-wood oil should be used over and over 

 again, as it becomes saturated with silver nitrate. 



893. Mounting. As pointed out in 881, Golgi preparations do 

 not keep well if mounted under a cover-glass in the usual way. 

 How and why this happens it is very difficult to say. Though an 

 elaborate discussion between SEHRWALD (Ztschr. iviss. Mikr., vi, 

 1889, p. 443), SAMASSA (ibid., vii, 1890, p. 26), and FISH (ibid., viii, 



1891, p. 168) has furnished the net practical result that watery 

 fluids should be avoided as much as possible during the after- 

 treatment, it is not clear why preparations should deteriorate, when 

 mounted under a cover-glass in thick cedar-wood oil or neutral 

 balsam ; while MANN (op. cit., p. 277) states, on the other hand, that 

 sections keep well if mounted under a cover-glass in Price's No. 1 

 pure neutral glycerin. 



For these reasons the general practice is to mount sections 

 without a cover, either on ordinary slides or on cover-glasses to be 

 inverted for study over the aperture of a hollowed-out wooden 

 slide. 



If mounting under a cover is desirable, this should either be raised 

 free of contact with the slide by means of wax feet or the like, or the 

 balsam of the mount should be rendered perfectly anhydrous by care- 

 ful heating it on the slide with the section in it, until it immediately 

 sets hard on cooling, when a slightly- warmed cover can be applied. 

 This last method is also recommended by HUBER (Anat. Anz., vii, 



1892, p. 587). B. LEE (see previous editions) advises keeping the 

 preparations uncovered until the sections have become quite dry 

 and the balsam, applied from time to time in thin layers, quite 

 hard, and then to cover them with a warmed cover-glass, this 

 being slightly pressed down on the sections. 



Various processes have been devised for mounting Golgi's prepara- 

 tions at once under a cover, but none of them give really satisfactory 

 results. One should have recourse to them either for special objects, or 

 if counterstaining with carmine or haematoxylin, or by Weigert-Pal's 



