INDULIN. 89 



may be mounted either in glycerin or balsam. " Lichtblau " is possibly a 

 synonym of this colour. The principal use of such a colour is for making 

 double stains. 



123 a. Carmine Blue (Bleu Carmin Aqueux). This colour is much 

 recommended by GILSON, into whose laboratory it was introduced by 

 JANSSENS. See La Cellule, vii, 1891, p. 347. 



124. Bleu de Lyon (Bleu de Nuit, Griinstichblau). I quote this 

 colour here, although 1 am not sure to what extent it is a pure plasmatic 

 stain. It is said to be very useful for double-staining with carmine. 



125. Indulin (Nigrosin, Bengalin, Anilin Blue-black, Blackley 

 Blue, Artificial Indigo). (Introduced by Calberla, see Morpli. Jahrb., 

 iii, 1877, p. 627.) Indulin dissolves into a dark blue solution in warm 

 water or in dilute alcohol. For staining, the concentrated aqueous solution 

 should be diluted with six volumes of water. Sections will stain in the 

 dilute solution in five to twenty minutes ; they may be washed in water or 

 in alcohol, and examined either in glycerin or oil of cloves. 



The peculiarity of this stain is that it never stains nuclei ; the remaining 

 cell- contents and intercellular substance are stained blue. In its general 

 effects it resembles quinolein blue, and is exactly the opposite of methyl 

 green. The stroma of tendinous tissue, for instance, stains of a fine blue, 

 the connective tissue that surrounds the bundle hardly at all, and the 

 tendon-corpuscles of Ranvier remaining perfectly colourless, stand out as 

 white stellate figures on a blue ground. 



126 Quinolein Blue (Cyanin, Chinolinblau ; v. Kanyier, Traite, 

 p. 102). Quinolein should be dissolved in alcohol of 36 strength (i. e. 90 

 per cent.), and the solution diluted with an equal volume of water. (If the 

 alcohol were taken dilute in the first instance the blue would not dissolve.) 

 The solutions employed for staining should be very weak, as quinolein 

 stains very powerfully. 



After staining, wash and mount in glycerin. When first mounted, nuclei 

 will be seen to be stained a fine violet, nerves of a grey-blue, smooth muscle 

 blue, protoplasm blue, fat deep blue. But after twenty-four hours in the 

 glycerin the aspect of the preparation is changed ; the nuclei have become 

 colourless ; the protoplasm remains blue, and is seen to contain granulations 

 stained intensely blue; nerves remain grey-blue, but frequently contain 

 granulations stained blue. Quinolein, in a word, has the property of 

 staining fatty matters an intense blue. 



If the stained preparations be treated with solution of potash of 40 per 

 cent, strength, the differential reaction is produced immediately ; the nuclei 

 are unstained, protoplasm, nerve, and muscle-tissue are pale blue, and fatty 

 matters deep blue. 



Quinolein is useful for staining Infusoria, which in dilute solution it 

 stains during life. On this point see the methods of Certes (post, Part II). 



127. Benzoazurin may be made to give either a diffuse or a 



