Phenyl Methane Dyes 



149 



other in hue that it takes very careful comparison to distinguish 

 one from another, and for many purposes they may be used inter- 

 changeably. 



The basic fuchsins are among the most powerful nuclear dyes, 

 and find many biological uses. They are valuable stains for mucin, 

 for elastic tissue, and for bringing out the so-called fuchsinophile 



.8- 



o 

 o 



L I I I I I I I I I I I I I I J 

 430 460 490 520 550 580 



WAVELENGTH m>l 



Fig. 20. Spectral curves of two rosanilins: 

 1. Basic fuchsin. 2. Acid fuchsin. 



granules. A basic fuchsin is often employed for staining the nu- 

 clear elements of the central nervous tissue. This group of dyes is 

 almost indispensable in bacteriology, particularly in the Ziehl- 

 Neelsen method, with its various modifications, for differentiating 

 the tubercle organism and thus making possible the diagnosis of 

 tuberculosis. 



