162 Biological Stains 



It has been called for by Bowie (1924) in a neutral stain com- 

 bination with Biebrich scarlet to stain the islets of Langerhans. 

 Kernohan (1931) and Proescher (1934) have each employed it in 

 staining nervous tissue; while Ono (1934) uses it for staining 

 spirochaetes in blood. 



n40 methyl green C. I. NO. 684 



Synonyms: Double green SF. Light green. 



Methyl green is crystal violet into which a seventh methyl group 

 has been introduced by the action of methyl chloride or methyl 

 iodide upon it, forming the compound:* 



CH3 CI 



\l 



N. 

 / 



CHa 



C26H33N3CI2; MoL Wt. 458.462 

 {A basic dye; absorption maximum 630-63 J^^ [J^20]) 



As the seventh methyl group is very loosely attached, there is 

 always some methyl or crystal violet present, either because it is 

 not all converted into the higher homolog or because it has broken 

 down again. It has been stated that to obtain free methyl green 

 the commercial dye should be shaken in a separatory funnel with 

 amyl alcohol or chloroform, which dissolves the methyl violet. As 

 a matter of fact, however, pure methyl green may not always be 

 desired by the biologist, as the dye owes part of the metachromatic 

 properties for which it is prized to the presence of small amounts of 

 the violet compound. 



Methyl green is at present one of the most valuable nuclear 

 stains known to the histologist, and is widely used as a chromatin 

 stain by the cytologist. On the other hand it has been used by 

 Galeotti as a cytoplasm stain following acid fuchsin and picric 

 acid; (see Krause, 1926-7, p. 1417). In the Ehrlich-Biondi technic 

 it is used to stain nuclei in contrast to acid fuchsin; (Id. p. 457); 

 while Bensley employs it to stain chromatin in contrast to acid 



"This ordinarily occurs in trade as a zinc chloride double salt. 



