ing fibrin and neuroglia. The bacteriologist also finds it a useful 

 stain and probably purchases more at the present time than all 

 other biologists together; the chief bacteriological use is in the 

 Gram technic for distinguishing between different kinds of bac- 

 teria. A further more recent use is in bacteriological media for in- 

 hibiting the growth of Gram-positive organisms, due to its selective 

 bacteriostatic action. 



The Flemming and Gram stains have seemed the most delicate 

 procedures for which it is used; so they have been given the most 

 careful study. In the case of the Gram stain it was discovered that 

 there are a score or more different procedures all referred to by the 

 name "Gram" stain, and a study was made of all the methods that 

 were found (see Hucker and Conn 1923). The result of the in- 

 vestigation is to conclude without reservation that crystal violet 

 may be substituted for gentian violet in both the Gram and Flem- 

 ming technics, and probably for gentian or methyl violet in any of 

 the bacteriological or histological methods for which either stain 

 is designated. If crystal violet can be used in all cases, the ad- 

 vantage is obvious; for it is a definite chemical compound, while 

 methyl and gentian violet are both variable mixtures. 



It is of interest to note that in the literature of microscopic tech- 

 nic crystal violet has been specified instead of gentian violet for 

 some special procedures. Worth noting is Benda's crystal-violet- 

 alazirin method for staining chondriosomes, and its modifications 

 by Meves and Duesberg; and also its use in combination with 

 erythrosin by botanists for staining lightly lignified walls, in which 

 technic it proves more uniform than gentian violet. 



GENTIAN VIOLET 



A poorly defined mixture of violet rosanilins is well-known to 

 biologists under the name gentian violet. The name is not used at 

 present in the dye or textile industries, however, and for this reason 

 the dye is not listed in dye indexes. It apparently applies to a 

 certain mixture containing about half dextrin and half dye, the 

 dye being a methyl violet, that is a mixture of crystal violet with 

 lower homologs of the same series. The statement has been made 

 and often repeated in biological literature that gentian violet is a 

 mixture of crvstal and methvl violet; but the looseness of the state- 

 ment is evident when it is realized that crystal violet is a component 

 of all the deeper shades of methyl violet. It is possible that before 

 the war gentian violet did represent a fairly constant mixture, but 

 there seems to be some doubt even on this point. It is certain that 

 since the war each company has used its own judgment as to what 

 to furnish when gentian violet is ordered. One company admits 

 furnishing crystal violet unmodified under this name; another 

 claims to be supplying penta-methyl-pararosanilin for gentian 

 violet; another apparently has been mixing crystal violet and 



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