98 CARMINE AND COCHINEAL STAINS. 



mulae given in the following pages I have been guided by the considerations 

 set out in 147. The best stains for staining in the mass are fully treated, 

 the old-fashioned solutions proposed for staining sections being thrown into 

 the background. The formulae set out below are arranged according to the 

 nature of the menstruum. This gives us two great groups, aqueous carmine 

 solutions and alcoholic carmine solutions. Taking first the group of aqueous 

 solutions, I have arranged the formulae comprised in it according to the 

 reaction of the solutions. 



The first subdivision comprises the acid solutions, i. e. those with free acid or 

 acid salts. The second subdivision comprises the so-called neutral carmines 

 and the alkaline solutions. These last are scantly treated, the very fact of a 

 staining solution having an alkaline reaction and at the same time an aqueous 

 menstruum implying that it must have a deleterious effect on tissues. Such 

 stains should be reserved for tissues that have in the process of harden- 

 ing been overcharged with chrome salts to such an extent as to no longer 

 take up other stains, and for maceration preparations, for which they may 

 sometimes be found useful. The alcoholic group is too small to require sub- 

 division. 



A. AQUEOUS CARMINE STAINS. 

 a. Acid. 



151. Mayer's Carmalum (Mitth. Zool. Stat. zu Neapel, 10, 3, 

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

 water, 200 c.c. Dissolve with heat. Decant or filter. Add some 

 antiseptic, either a few crystals of thymol, or 1 per cent, salicylic 

 acid, or 5 per cent, salicylate of soda. The solution will 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. 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 155. 



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. It should be noted that with either 

 solution the objects to be stained should not have an alkaline 

 reaction. 



152. MAYER'S Aqueous Carminate- of- Alumina- Solution (Mitth. 



