EOSIN. 91 



1888, p. 466) says that Benzopurpurin B. is the very best 

 contrast stain to hsematoxylin known to him. It seems to 

 him preferable to eosin on account of its not being affected 

 by alcohol or the usual clearing agents. Weak aqueous 

 solutions should be used for staining, which is effected in a 

 few minutes, and alcohol for washing out. Deltapurpurin, a 

 more purple red, has similar properties, and may be used in. 

 the same way. The solution (aqueous) should be moderately 

 concentrated, and allowed to act for a minute or two. 



134. Biebricher Scharlach (BIEBEICH SCAELET), a diffuse bright red 

 stain, may be useful as a contrast stain. See Griesbach, Arch. f. mik. Anat.> 

 xxii, p. 132. 



135. Eosin, the potassium salt of a bromide of phthalein, is 

 found in commerce under the synonyms of Primerose Soluble, 

 Erythrosin, Pyrosin B., Rose B. a 1'Eau. The preparations 

 indicated by these names are not quite identical in their pro- 

 perties, but vary according to the different modes of manu- 

 facture. Most of them are soluble both in alcohol and in 

 water, but some only in alcohol ("Primerose a I' Alcohol"). 



Eosin is of very great importance as a secondary or contrast 

 stain. It has already been mentioned that it washes out 

 many of the anilins that give nuclear stains by the indirect 

 method (see 98) . Combined with a blue anilin, or with 

 haematoxylin, it gives instructive and durable double stains, : 

 which are among the most beautiful that can be produced. 

 These will be treated of in the chapter on double stains. 

 Here it may merely be mentioned that the majority of the 

 authors who recommend these combinations proceed by stain- 

 ing first with the eosin and then with the nuclear stain, and 

 that the majority also employ alcoholic solutions of eosin. I 

 am by no means convinced that this practice is the best. As 

 regards the anilins, at all events, good results are certainly 

 obtained by staining first with the nuclear stain (gentian 

 yiolet, for instance) and washing out (sections) for a few 



seconds or a minute or two in a tolerably strong aqueous solu- 

 tion of eosin, and then dehydrating with alcohol and mounting 

 in balsam. If the eosin is too much extracted by the alcohol 

 or clearing agent, these should be used charged with a little of 

 the colour. Eosin stains may also be kept in glycerin, if this 

 be perfectly neutral or, better, slightly alkaline (which may 



