CARMINE AND COCHINEAL STAINS. 167 



quantity of inorganic impurities, or being hygro- 

 scopic, or being too dear. 



A. AQUEOUS CARMINE STAINS. 

 a. Acid. 



211. MAYER'S Carmalum (Mitth. Zool. Stat. zu Neapel, x, 

 3, 1892, p. 489). Carminic acid, 1 grm. ; alum, 10 grms. ; 

 distilled water, 200 c.c. Dissolve with heat (if necessary : 

 I have been able to make my solutions in the cold) . Decant 

 or filter. Add some antiseptic, either a few crystals of 

 thymol, or 0*1 per cent, salicylic acid, or 0'5 per cent, salicy- 

 late of soda. The solution mil then keep. A clearish red 

 fluid with a violet tinge. It stains well in bulk even osmium 

 objects. If washed out with distilled water only, the plasma 

 will remain somewhat stained. If this be not desired, wash 

 out carefully with alum solution, or, in difficult cases, with 

 weak acid, followed in either case with water. The general 

 effect is that of an alum-carmine stain. A notable difference 

 between the two is that carmalum stains well in bulk, which 

 alum -carmine is not very suitable for when used in the 

 ordinary way ; but see 215. 



A weaker solution may be made by taking from three to five times as 

 much alum and five times as much water, and dissolving in the cold, which 

 may be convenient. This is a very close equivalent of alum-carmine, 

 giving, however, a somewhat redder stain. I find this solution very weak 

 for ordinary work. 



With either solution the objects to be stained should not 

 have an alkaline reaction. The other properties of these 

 solutions are very similar to those of alum-carmine. 



UAWITZ (Anat. Am., xv, 1899, p. 438) takes 2 grms. carminic acid, 20 

 grms. ammonia-alum, 150 c.c. water, and 150 c.c. glycerin. A strongly 

 staining solution which keeps well. He recommends it only for sections. 

 Mayer does not admit the supposed advantages of the ammonia-alum. 



212. MAYER'S Aqueous Aluminium-Chloride-Solution (Mitth. Zool. 

 Stat. zu Neapel, x, 3, 1892, p. 490). Carminic acid 1 grm., chloride of 

 aluminium, 3 grms.; water 200 c.c. Add an antiseptic, as for carmalum. 



CM.- as carmalum. The stain is of a blue-violet colour, very powerful, 

 and elective. But it is not so pure a stain as that of carmalum, plasma 



