168 CHAPTER XII. 



being more strongly coloured. It is recommended only as a substitute for 

 carmalum in cases in which the latter is counter-indicated on account of the 

 presence of alum or the like. 



213. Alum-carmine (GRENACHER'S formula, Arch. mik. Anat., 

 xvi, 1879; p. 465). An aqueous solution (of 1 to 5 per cent. 

 strength, 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 con- 

 centrated 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 struc- 

 tures that it is wished to preserve. 



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

 Ospetali, No. 24 ; Zeit. f. wiss. Mik., ii, 1885, p. 378), and GEIEB (Mem. 

 Soc. Ital. Sci., t. vi, No. 9, 1887; Zeit. /. wiss. Mik., vii, 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 grms. 

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

 sets some carminic acid free. The same result may be obtained by adding 

 carminic acid to alum -carmine or carmalum. 



Alum-carmine is one of the best stains to be found outside 

 the coal-tar colours. It is particularly to be recommended 

 to the beginner, as it is easy to work Avith ; it is hardly 

 possible to overstain with it (except muscle). Its chief defect 

 is that it is not very penetrating, and therefore quite 

 unsuitable for staining objects of considerable size in bulk. 

 This defect may, however, be to some extent overcome by 

 employing the acid formula of Henneguy ( 215), if it be not 

 convenient to use Mayer's carmalum. 



The stain is permanent in balsam; as to aqueous media 1 

 cannot say. 



214. Cochineal Alum-carmine (PARTSCH, Arch. f. mik. 

 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 juldi-d to preserve it from mould. 



Another method of preparation has been given by CZOKOR (Arch. f. mik. 

 Anat., xviii, 1880, p. 413). Mayer has carefully examined both, and finds 



