264 CHAPTER XIX. 



369. Purpurin, see RANVIER'S Traite technique, p. 280; DUVAI/S 

 Precis de Technique histologique, p. 221 ; and GEENACHEE'S formula in 

 Arch. f. mik. Anat., xvi, 1879, p. 470. 



370. Indigo. Indigo is employed in histology in the form of solutions 

 of so-called indigo-carmine, or snlphindigotate of soda or potash. The 

 simple aqueous solution gives a diffuse stain, and is therefore not capahle 

 of being usefully employed alone. It is, however, of use when employed 

 to bring about a double stain in conjunction with carmine, see below. 



Thiersch's Oxalic Acid Indigo-carmine (see Arcli.f. mik. Anat., i, 

 1865, p. 150). 



Carmine Combinations. 



371. Seiler's Carmine followed by Indigo - Carmine (Am. 

 Quart. Mic. Journ., i, 1879, p. 220; Journ. Roy. Mic. Soc., ii, 1879, 

 p. 613). Stain in borax-carmine, wash out with HC1 alcohol, wash out the 

 acid, and after-stain in an extremely dilute alcoholic solution of indigo- 

 carmine (two drops of saturated aqueous solution added to an ounce of 

 alcohol and filtered). 



I find this method gives good results when applied to sections, but very 

 bad results if it be attempted to stain in the mass with the indigo. The 

 indigo overstains the superficial layers before it has penetrated to the 

 deeper layers. The instructions given refer to sublimate material or the 

 like ; I find chroin-osmiurn material will not take the stain at all. 



372. Merkel's Carmine and Indigo -Carmine in One Stain 

 (MEBKEL, Unters. a. d. anat. Anst. Rostock, 1874; Month. Mic. Journ., 

 1877, pp. 242 and 317). 



Also NOBRIS and SHAKESPEARE, Amer. Journ. Med. Sc., January, 1877 ; 

 MEEKEL, Mon. Mic. Journ., 1877, p. 242 ; MARSH, Section Cutting, 

 p. 85; BAYEEL, Arch. f. mik. Anat., xxiii, 1885, pp. 36, 37; MACALLUM, 

 Trans. Canad. Instit., ii, 1892, p. 222 ; Journ. Roy. Mic. Soc., v, 1892, 

 p. 698. 



MERKEL'S formula, as has been pointed out by PAUL MAYER (Mitth. Zool. 

 Stat. Neapel, xii, 2, 1896, p. 320) is not only highly irrational, and incon- 

 venient to employ, but gives an alkaline fluid that may be injurious to 

 tissues. I agree with him that it should be suppressed. 



373. P. MAYER'S Carmalum (or Haemalum) and Indigo-Car- 

 mine in One Stain. In the place quoted in the last section, 

 MAYER states that he obtains very good results by taking a 

 solution of O'l gramme of indigo-carmine in 50 c.c. of dis- 

 tilled water, or 5 per cent, alum solution, and combining it 

 with from four to twenty volumes of carmalum or haemalum. 



