COAL-TAR PLASMA STAINS. 221 



staining of Protozoa). I myself have had very good results 

 with it as an intra-vitam stain. 



It has also been found useful for staining, in hardened 

 material, the corpuscles of NISSL (q. v.) in nerve-cells. 

 These bodies are basophilous; hence, it is suggested, their 

 staining by neutral red, which is a "basic" colour. The 

 term " neutral ' refers to the hue of its solution, not to 

 its chemical composition. Its neutral red tint is turned 

 bright red by acids, yellow by alkalies. The stain in tissues 

 is in general metachromatic, nuclei being red, cell-bodies 

 yellow (cf. EOSIN, iu Deutsche med. Wochenschr., xxiv, 1898, 

 p. 615 ; Zeit. /. wiss. Mik., xvi, 2, 1899, 238). The solutions 

 that have been employed for staining fixed material are 

 strong aqueous ones, 1 per cent, to concentrated. See further 

 under NISSL, in the chapter on " Neurological Methods." 



297. Biebricher Scharlach (BIEBRICH SCARLET), a diffuse bright red 

 stain, may possibly be useful as a contrast stain. See GRIESBACH, Arch. f. 

 mile. Anat., xxii, p. 132. 



298. The Eosins, found in commerce under the names of 

 Eosin, Saffrosin, Primerose Soluble, Phloxin, Bengal Rose, Ery- 

 throsin, Pyrosin B, Rose B, a 1'Eau, etc., are all phthalein 

 colours. The preparations indicated by these names are not 

 quite identical in their properties, but vary according- to the 

 different modes of manufacture. Most of them are soluble 

 both in alcohol and in water, but some only in alcohol ("Pri- 

 merose a I' Alcohol"). 



They are all diffuse stains, formerly much used as con- 

 trast stains, less so now. 



Their chief use is in combinations or mixtures, to be given 

 further on. For Bengal Rose see GRIESBACH, Zool. Anz., 

 No. 135, 1883, p. 172. 



Eosin is a specific stain for red blood-corpuscles, and also 

 for certain granules of leucocytes, and hence is much used 

 in the study of blood, for which see in Part II. 



The yolk of some ova takes the stain strongly, so that it 

 is useful in some einbryological researches. 



299. Methyl Green and Eosin (CALBERLA, Morph. Jahrb., iii, 1877, 

 Heft 3, p. 625; LIST, Zeit.f. tviss. Mil:., ii, 1885, p. 147; BALBIANI, Ann. 

 Microgr., Paris, vii, 1895, p. 245; RHUJIBLER, Zeit. wiss. Zool., Ixi, 1895, 

 p. 38). See previous editions. 



