288 STAINS AND STAINING. 



Carmine. 



Carmine is also used as a nuclear stain, and the two solutions 

 more generally employed are Grenadier's alcoholic borax carmine 

 and Orth's lithium carmine. Under ordinary circumstances they 

 act as general stains, affecting the ground tissue as well as the 

 nuclei. By subsequent treatment with acidulated alcohol, or 

 acidulated glycerine, the colour is discharged from the ground 

 tissue without seriously affecting the nuclei. Used in this way, 

 carmine becomes a good nuclear stain. It should be remembered 

 that the sections must not be washed in pure water, as the colour 

 will be to a great extent removed, nor in acidulated water, as the 

 carmine will be precipitated on the sections. Alum carmine and 

 alum cochineal are useful nuclear stains not requiring after-treat- 

 ment with acid. I now add chloroform to the lithium carmine 

 and alum carmine solutions, to give them the keeping properties 

 of chloroform water. 



Picro-car7?iines. 



These have been largely used, and, in some quarters, are great 

 favourites. Ammonia, lithia, or soda, is used as the solvent for 

 the carmine, and a certain quantity of picric acid is added. 

 Several complicated formulae have been published for ammonia 

 picro-carmine ; I have tried the following, amongst many others, 

 and find it to be the best all-round solution. 



Ammonia Picro-carmine. 

 Carmine, i gramme ; strong solution of ammonia, 3 c.c. ; 

 distilled water, 5 c.c. Dissolve the carmine in the ammonia and 

 water with a gentle heat, then add saturated aqueous solution of 

 ])icric acid, 200 c.c. ; heat to boiling, and filter. 



Picro-Lithiu7n Carmifie. 

 Some workers prefer the picro-lithium carmine, and one of 

 them told me that he preferred to use the following proportions : 

 Lithium carmine solution, 1 00 c.c. ; saturated solution of picric 

 acid, 270 c.c. 



Aniline Nuclear Stains. 



There are several aniline dyes which are used for nuclear 

 staining : — methylene blue, methyl green, safranine, gentian violet, 



