PROTOZOA 583 



hjcmatoxylin and may be used in the same way. Chatton uses 

 it for peridinians after picric acid fixative {Arch. Zool. Expe'r., lix, 

 1920, p. 21), and Keilin {Parasit., xv, 1923, p. 103) for gregarines. 

 (B) Carmine stains are penetrating and useful for staining 

 protozoa, especially in blocks of tissue, before imbedding. 



1147. («) Grenacher's borax carmine (see § 271) contains 

 about 35 per cent, alcohol and is alkaline, and may, therefore, 

 harm delicate objects. Dobell (p. 6) says that " used warm, and 

 acidified with a small quantity of glacial acetic or hydrochloric 

 acid, it will often stain the contents of cysts when all other methods 

 have failed." One would expect, since the acid and borax are 

 incompatible, that paracarmine (see below) diluted with an equal 

 volume of water would be equally sat i(s factory. 



(6) Mayer's paracarmine, made up in 70 per cent, alcohol 

 (§ 273), may be diluted and slightly acidified, for staining whole, 

 especially large, protozoa. It is generally better to stain over- 

 night and wash out with acid alcohol, but sometimes twenty to 

 thirty minutes will be enough to give a good colour by the pro- 

 gressive method. 



(c) Alum carmine, aqueous solution (see § 254), is useful 

 for staining whole protozoa, also picro-carmine, § 266. 



{d) Hollande's iron-chloro-carmine (see § 259). A very 

 intense stain suitable for mitochondria and other cytoplasmic 

 inclusions in sections of protozoa after suitable fixation. 



1148. Hickson's iron Brazilin stain (Quart. Joiirn. Micr. Set., xliv, 

 1901, p. 469) may be used for protozoa after fixing in Schaudinn's fluid 

 for fifteen minutes and washing in 70 per cent, alcohol for at least an 

 hour. 



Mordant for one to four hours in 1 per cent, iron alum in 70 per cent, 

 alcohol, rinse in 70 per cent, alcohol and stain three to sixteen hours in 

 1 per cent, brazilin in 70 per cent, alcohol, then wash thoroughly in 

 several changes of 70 per cent. 



According to Carleton (p. 299) brazilin requires partly oxidising 

 into brazilein to give precise staining. 



1149. Safranin 0, especially after Flemming's fixative, is useful 

 for parasites, free or in tissues (see § 372). 



A solution in absolute alcohol is generally diluted with about 

 the same volume of water, or a saturated solution in water may 

 be used for a few minutes. The stain becomes brick-red when 

 subsequently treated with picric acid (see § 1158, below). It may 

 be differentiated with acid alcohol, picric acid, or clove oil. 



1150. Acid fuchsin (Magenta S, etc. ; see § 319) is generally 

 used in aqueous solution (0-5 per cent, to saturated) for a few 

 minutes. Preparations can be differentiated in tap-water, since 

 the stain easily washes out in alkalies. 



1151. Counterstains. Many stains, such as eosin, orange G, 

 light green, Bordeaux red, dissolved in 96 per cent, alcohol, are 



