158 



SCIENCE 



[Vol. liVI, No. 1441 



typhoid organisms. For staining bacteria sev- 

 eral satisfactory samples have been found, 

 namely, those obtained from Coleman and Bell, 

 Dicks, David & Co., the Goldin Biological Lab- 

 oratories, the H. S. Laboratories, National Ani- 

 line and Chemical Company, the Newport 

 Chemical Works and the Providence Chemical 

 Company. Used in the Endo medium all of 

 these samples have given as good results as 

 Griibler's basic fuchsin, but one of them, 

 namely, that of Coleman and Bell, gives even 

 better results for this purpose than Griibler's 

 samples or any of the others tested. 



GENTIAN VIOLET 



Gentian violet is not a textile dye. It is not 

 recognized in the regular dye industry and is 

 not listed in Schultz's index, the recognized list 

 of textile dyes. The name was apparently 

 introduced by Griibler and is certainly found 

 nowhere except in the literature relating to 

 biological stains. Griibler's gentian violet was 

 a mixture of various pararosanilin dyes, but its 

 exact composition is a little diiiicult to deter- 

 mine because of conflicting statements that 

 have been made about it. Somewhat simpler 

 mixtures of these pararosanilin dyes are known 

 to the textile trade under the name of methyl 

 violet, the name being followed by a designa- 

 tion indicating the shade such as B, 2B, 3B, etc. 



The methyl violets are regarded as being 

 various mixtures of the following three com- 

 pounds : Tetramethyl-pararosanilin, pentame- 

 thyl-pararosaniUn, hexamethyl-pararosanilin, 

 which differ from each other as the names imply 

 in containing 4, 5 and 6 methyl groups respec- 

 tively to the molecule. The more highly 

 methylated the compound, the bluer its shade, 

 and as in the trade designation of these dyes 

 the number of B's following the name indicates 

 the depth of the blue in the violet, it may be 

 assumed that the more highly methylated com- 

 pounds are distinguished bj' the greater number 

 of B's, although these trade designations do not 

 refer to definite chemical formulae. In the case 

 of methyl violet 5B, 6B and 7B, there is appar- 

 ently a still different compound introduced in 

 which one or more of the methyl groups have 

 been replaced by benzyl groups. 



Only two of these compounds have to our 

 knowledge been put upon the market in a pure 



form, namely, the pentamethyl and the hexa- 

 methyl compounds. The former of these has 

 been claimed to have been obtained pure for 

 use in microscopic work but has never been put 

 on the market widely. The latter is a well- 

 known textile dye sold under the name of 

 crystal violet. 



It will thus be seen that there are quite a vari- 

 ety of dyes and biological stains all falling with- 

 in the group commonly referred to by biologists 

 as gentian violet. Now that it is certainly dif- 

 ficult, and perhaps impossible, to obtain the 

 same mixture sold by Griibler as gentian violet, 

 it becomes a question just what to use in its 

 place. Certainly it is not wise to purchase 

 "gentian violet" at the present time, because 

 every dealer has his own idea as to what to sell 

 under this name and the different gentian vio- 

 lets at present on the market vary from pure 

 crystal violet to various mixtures of methyl 

 violets with crystal violet, some of them possi- 

 bly containing other dyes as well. 



The first point, therefore, that the committee 

 wished to test was as to what dye to substitute 

 for gentian violet. The work so far done along 

 this line has been mostly in connection with 

 the Gram staining technic, the procedure for 

 which the bacteriologist most frequently em- 

 ploys this stain. Work is at present in progress 

 to see whether the conclusions reached in this 

 work will apply also to this stain when used 

 for histological purposes. The indications are 

 that they will. 



It has been found that for the Gram stain 

 the compounds of low methyl-ation such as those 

 known under the names methyl violet, methyl 

 violet B and methyl violet 2B are rather unsat- 

 isfactory, but that methyl violet 5B and crystal 

 violet can be well substituted for gentian violet. 

 Now, crystal violet is a definite chemical com- 

 pound and is generally recognized as a textile 

 dye; hence, the source of supply is much more 

 constant than in the case of any of the other 

 dyes in this group, and it seems to be the most 

 logical substitute to use. The committee there- 

 fore recommends that, except for work where 

 it is known that crystal violet will not work, 

 this dye be substituted for gentian violet, and 

 that it be regularly substituted for it in the 

 Gram stain for bacteria. 



