286 CHAl'TER XXIV. 



Pigments (i. e. those iu question) dissolve in tliis fluid, and so doing- 

 form a stain whicli suffices in twelve to twenty-four hours for staining 

 the nuclei of the preparation. 



583. Nitric Aeid. — Paekbr (Bull. Mus. Comp. Zool., Cambridge, 

 U.S.A., 1889, p. 173) treats sections (of eyes of scorpions) fixed to the 

 slide with Schalliiiaum's medium, for about a minute with a solution of 

 up to 50 per cent, of nitric acid in alcohol, or, still better, with a 35 per 

 cent, solution of a mixture of equal parts of nitric and hydrochloric 

 acid in alcohol. To make the solution, the acid should be poured slowly 

 into the alcohol (not vice versa), and the mixture kept cool. 



Jandbk {Zeit. wiss. Mile, xv, 1898, p. 163) takes for removal of pig- 

 ments Seileb's chromo-nitric acid (§ 670) ; twelve to forty-eight hours 

 is enough for small objects. 



See also under " Arthropoda." 



584. Caustic Soda. — Rawitz (Leitfaden, p. 29) dissolves the pigment 

 of the mantle of Lamellibranchia by means of 3 to 9 drops of officinal 

 caustic soda solution added to 16 to 20 c.c. of 96 per cent, alcohol. 



