204 METALLIC STAINS 



SzuTZ {Zeit. wiss. Mik., xxix, 1912, p. 291) in glycerin with -^o of 

 formol. 



Sattler {Arch. mik. Anat., xxi, p. 672) exposes to the light for 

 a few minutes in water acidulated with acetic or formic acid. 



Thanhoffer {Das Mikroskoij, 1880) employs a 2 per cent, 

 solution of acetic acid. 



Krauss brings his preparations, after washing, into a light 

 red solution of permanganate of potash. Reduction takes place 

 very quickly, even in the dark. 



Oppitz puts for two or three minutes into a 0*25 or 0-50 per 

 cent, solution of chloride of tin. 



Jakimovitch {Journ. de VAnat., xxiii, 1888, p. 142) brings 

 nerve preparations, as soon as they have become of a dark brown 

 colovu', into a mixture of formic acid 1 part, amyl alcohol 1 part, 

 and water 100 parts, and exposes to the light for five to seven 

 days, the mixture being renewed from time to time. 



Dekhuyzen {op. cit., last §) reduces in oil of cloves, after 

 dehydration. 



394. Fixation. Legros {Journ. de VAnat., 1868, p. 275) washes his 

 preparations, after reduction, in hyposulphite of soda, to prevent after- 

 blackening. According to Duval {Precis, p. 230) they should be washed 

 for a few seconds only in 2 per cent, solution and then in distilled water. 



Gerota {Arch. Anat. Phys., Phys. Abth., 1897, p. 428) reduces in a 

 hydroquinone developing solution, followed by fixation in hyposulphite 

 of soda, just as in photography. 



395. Impregnation of Marine Animals. On account of the 

 chlorides that bathe the tissues of marine animals, these cannot 

 be treated directly with nitrate of silver. 



Hertw^ig {Jen. Zeit., xiv, 1880, p. 322) recommends fixing 

 them with a weak solution of osmic acid, then washing with dis- 

 tilled water until the wash-water gives no more than an insigni- 

 ficant precipitate with silver nitrate, and then treating for six 

 minutes with 1 per cent, solution of silver nitrate. 



Harmer {Mitth. Zool. Stat. Neapel, v, 1884, p. 445) washes 

 them for some tiine (half an hour) in a 5 per cent, solution of 

 nitrate of potash in distilled water ; they may then be treated 

 with silver nitrate in the usual way. For some animals he recom- 

 mends a 4-5 per cent, solution of sulphate of soda. 



396. Double-staining Silver-stained Tissues. The nuclei of 

 tissues impregnated with silver may be stained with the usual 

 reagents, provided that solutions containing free ammonia be 

 avoided. These stains will only succeed, however, with successful 

 negative impregnations, as nuclei that have been impregnated 

 will not take the second stain. 



Impregnation with silver may be followed by impregnation 

 with gold. In this case the gold generally substitutes itself for 

 the silver in the tissues, and though the results are sharp and 



