CAltMlNE AND COCM IN lv\ I, STAINS. 143 



or any other strength that may be preferred) of common or 

 ammonia alum is boiled for ten or twenty minutes with ^ to 

 1 per cent, of powdered carmine. (It is perhaps the safer 

 plan to take the alum solution highly concentrated in the 

 first instance, and after boiling the carmine in it dilute to 

 the desired strength.) When cool, filter. 



This stain must be avoided in the case of calcareous 

 structures that it is wished to preserve. 



TIZZONI (Bull. Sc. Mcd, Bologna, 1884, p. 259), PISENTI (Gazz. degli 

 Otpetali, No. 24; Zeit. wiss. Mil:., ii, 1885, p. 378), and GRIEB (Mem. 

 Soc. Ital. Sci., t. vi, No. 9, 1887; Zeit. wiss. Mik.,vu, 1, 1890, p. 47) 

 have given modifications of Grenadier's formula which do not appear 

 to me rational. 



MAYER (ibid., xiv, 1897, p. 29) makes a stronger stain by taking 2 

 grins, carmine, 5 grins, alum, and 100 c.c. water, and boiling for an hour. 



Alum-carmine is an excellent stain. It is particularly 

 to be recommended to the beginner, as it is easy to work 

 with ; it is hardly possible to overstain with it. Its chief 

 defect is that it is not very penetrating, and therefore 

 unsuitable for staining objects of considerable size in bulk. 



215. Acetic Acid Alum-Carmine (HENNEGUY, in Traitu des 

 Meth. techn., LEE et HENNEGCY, 1887, p. 88). Excess of car- 

 mine is boiled in saturated solution of potash alum. After 

 cooling add 10 per cent, of glacial acetic acid, and leave to 

 settle for some days, then filter. 



For staining, enough of the solution is added to distilled 

 water to give it a deep rose tint. In order to ensure rapid 

 diffusion it is well to bring the tissues into the stain direct 

 from alcohol. Stain for twenty-four to forty-eight hours, 

 and wash for an hour or two in distilled water. Mount in 

 balsam. You can mount in glycerin, but the preparations 

 do not keep so well. 



The advantage of this carmine is that it has much greater 

 power of penetration than the non-acidified alum-carmine. 



216. Cochineal Alum-carmine (PARTSCH, Arch. mik. Anat., 

 xiv, 1877, p. 180). Powdered cochineal is boiled for some 

 time in a 5 per cent, solution of alum, the decoction filtered, 

 and a little salicylic acid added to preserve it from mould. 



Another method of preparation has been given by CZOKOK 



