220 CHAPTER XVI. 



it useful in staining axis-cylinders. See the chapter on Nerve Tissue, in 

 Part II. It may also be used for staining some objects during life (see 

 ante, 201). 1 have tried it as a general plasma stain, and cannot recom- 

 mend it, as the stain does not keep. CAENOY (La Cellule, xii, 2, 1897, 

 p. 216) has, however, had very good results with it as a secondary stain 

 employed after hamatoxylin of DELAFIELD, and found the stain keep 

 well. He used a O'o per cent, solution in water. Note that this colour 

 is not to be confounded with other Congos, as Congo yellow, or Brilliant 

 Congo. 



LOISEL (Journ. de I'Anat. et de la Phys., 1898, p. 230) says concerning 

 the reaction with free acids, that the colour is azure-blue with mineral 

 acids and dark violet with organic acids. In the presence of chlorine 

 compounds it gives the same reaction as with acids. In the presence of 

 ammoniacal liquids it will not give the reaction with C0 2 nor with acetic or 

 lactic acid. See WUESTEE, Centralb.f. PhysioL, 1887, p. 240. 



295. Benzopurpurin. According to GEIESBACH (loc. cit.), another 

 "acid" colour very similar in its results to Congo red. It has been commended 

 as a plasma stain. I have myself been unable to obtain any results what- 

 ever with it. See, however, ZSCHOKKE (ibid., v, 4, 1888, p. 466), who recom- 

 mends Benzopurpurin B, and says that weak aqueous solutions should 

 be used for staining, which is effected in a few minutes, and alcohol for 

 washing out. Deltapurpurin has, it is said, similar properties, and may 

 be used in the same way. 



296. Neutral Red (Neutralroth) (EHRLICH, Allg. med. Zeit., 

 1894, pp. 2, 20; Ze-it.f. >iciss. Milc.,xi, 2, 1894, p. 250; GALEOTTI, 

 ibid., p. 193). Up to the present this colour has chiefly 

 been employed for intra-vitam staining. Tadpoles kept for a 

 day or two in a solution of 1 : 10,000 or 100,000 absorb so con- 

 siderable a quantity of the colour that all their tissues appear 

 of a dark red. The stain is limited to cytoplasmic granules 

 (EHRLICH), and to the contents of mucus cells (GALKOTTI). 



S. MAYER (Lotos, Prague, 1806, No. 2) states that it also 

 stains degenerating myelin. According to a further study 

 of this colour by EHRLICH and LAZARUS (Spec. Pathol. und 

 Therapie, herausgeg. von NOTHNAGEL, viii, 1, 1898, p. 1 ; 

 Zeit. f. wixs. Mile., xv, 3, 1899, p. 338) it may be used for 

 intra-vitam staining of tissues in the same way us methylen 

 blue (next chapter), by injection or immersion with contact 

 of air. It is especially a granule stain. Similar results are 

 recorded by ARNOLD (Anat. Anz., xvi, 1899, p. 568). See 

 also LOISEL (Journ. de VAnat. et de la PhysioL, 1898, 

 pp. 197, 210, 217) (intra-vitam staining of sponges) ; and 

 PROWAZEK, Zeit. f. wiss. ZooL, Ixii, 1897, p. 187 (intra-vitam 



