Phenyl Methane Dyes 



145 



ably less subject to fading. Slides have been exposed to direct 

 sunlight for a few weeks and have still retained the green color. 

 This dye is therefore to be recommended for such use as it has all 

 the advantages of light green without the disadvantages. Con- 

 sidering the comparatively short period of time since this dye was 

 first introduced to the microscopist, it is now employed in a sur- 

 prisingly large number of procedures, among which might be men- 

 tioned the following as illustrating two widely different types of 



.7- 



N.6- 



o 

 H 



O 



.5- 



£.3- 



UJ 



o 



O 



o 

 o 



380 



I I I I I I 



440 500 560 620 

 WAVELENGTH TTI^A 



I J 



680 



Fig. 19. Spectral curves of three phenyl methane dyes: 

 1. Methyl green. 2. Light green SFY. 3. Fast green FCF. 



methods: the quadruple staining technic of Johansen (1939), for 

 plant histology, in which it is combined with safranin, methyl 

 violet, and orange G; its use as a bacterial stain by Maneval, 

 (1941), who recommends this and other acid dyes (e.g. acid fuch- 

 sin, aniline blue W.S., and orseilline) as preferable to the conven- 

 tional basic dyes because of the better diflFerentiation afforded and 

 the less tendency for slime and debris to take the stain. 



