180 Biological Stains 



%io 



This dye differs from pyronin Y only in that it is an ethyl in- 

 stead of a methyl derivative. As a result it is very slightly deeper 

 in shade but has almost identically the same staining behavior. 

 The two dyes have very similar spectral curves, as shown by the 

 graphs in Fig. 23. 



The pyronins find their principal use in the Pappenheim (1899) 

 combination, where a pyronin is employed with methyl green for 

 staining basophile elements, especially the mast cells, and for stain- 

 ing the gonococcus in smears of pus. It is also used sometimes as a 

 counterstain in the Gram technic for bacteria (see p. 160); and by 

 Ehrlich and Lazarus (1898) as a component of certain "neutral" 

 stains. Monn^ (1938) has employed a pyronin for staining mito- 

 chondria; while Huddleson (1931) makes use of its bacterio- 

 static properties in distinguishing between species of the bacterial 

 genus, Brucella. 



For technic of Pappenhelm-Saathof stain for gonorrhoeal pus, see Staining Pro- 

 cedures,* p. IIIA2-I9. 



For technic of Saathof stain for bacteria in tissues, see Id. p. IIIBj-o. 



2. THE RHODAMINES 



The rhodamines are similar to the pyronins except that there is 

 a third benzene ring attached to the central carbon atom arid 

 attached to this ring is a carboxyl group in the ortho position. 

 This latter group, although of acid tendency, does not counteract 

 the basic action of the amino groups, so the dyes are basic in 

 character. 



♦Conn and Darrow (1943-4). 



