188 CHAI'TEU XV. 



Picric acid has considerable power of washing out other 

 anilin stains ; and in combination icith hydrochloric acid it 

 very greatly enhances the power with which this acid washes 

 out carmine stains. It should, therefore, not be added to 

 the acidulated alcohol taken for differentiating borax-carmine 

 stains, or the like, but only to the neutral alcohol used after- 

 wards. It has the great quality that it can be used for 

 staining entire objects, and is much indicated for such 

 objects as small Arthropods or Nematodes, mounted whole. 



It can in some cases be employed by dissolving it in the 

 solution of another dye (see Picro-carmine, LEGAL'S alum- 

 carmine, 219, etc.) ; or (for sections) by dissolving it in the 

 xylol or chloroform used for clearing. 



Though picric acid is a useful ground stain, it is at most a 

 rough one, being very diffuse. It stains, however, horn, 

 chitin, muscle and erythrocytes, with special energy. 



According to FROHLICH (Zeit. u-iss. Mik., xxvii, 1910, 

 p. 31-9) picraminic acid (from Grubler & Hollborn) has some 

 advantages over picric acid. 



299. VAN GIBSON'S Picro-Saurefuchsin (from Zeit. wiss. Mik., 

 xiii, 1896, p. 344). To a saturated aqueous solution of 

 picric acid is added a few drops of saturated aqueous 

 solution of Saurefuchsin, until the mixture has become 

 garnet-red. Or (Trans. Amer. Micr. Soc., xix, 1898, p. 

 105) to 100 parts of the picric. acid solution add 5 parts of 

 1 per cent, solution of Saurefuchsin. After staining (sections 

 only), rinse with water, dehydrate, and clear in oil of 

 origanum. 



OHLMACHEK (Joitrn. Exper. Med., ii, 1897, p. 675) adds 0'5 

 per cent, of Saurefuchsin to a saturated solution of picric 

 acid which has been diluted with an equal quantity of water. 

 He uses this after previous staining with gentian violet. 



RAMON Y CAJAL recommends O'l grm. of Saurefuchsin to 

 100 of saturated solution of picric acid (SCHAFFER, Zeit. wiss. 

 ZooL, Ixvi, 1899, p. 236). 



HANSEN (Anat. Anz., xv, 1898, p. 152) adds 5 c.c. of 2 per 

 cent, solution of Siiurefuchsin to 100 c.c. saturated solution 

 of picric acid, ;md for staining adds to 3 c.c. of the mixture 

 one third of a drop of 2 per cent, acetic acid, stains for a 

 few minutes or hours, rinses in 3 c.c. of water with 2 drops 



