NEW METHOD FOR GRAM STAIN 181 



ing the films in sodium bicarbonate or lactic acid greatly affects 

 the result. 



7. The addition of sodium bicarbonate results in a greater con- 

 centration of the methyl violet dye being present in the Gram 

 positive organisms after decolorization and lactic acid brings 

 about the opposite result. The failure of Gram positive organ- 

 isms in old cultures and in smears from the genital-urinary tract 

 to retain the violet dye may be due in part to the presence of 

 certain acids. These facts suggest the possibility of enhancing 

 the value of gentian violet in selective media and improving 

 dye therapy by the addition of an alkali. 



8. All of the colon-typhoid group of organisms do not differ 

 from the gonococcus-catarrhalis group of organisms in their resist- 

 ance to the penetration of the methyl violet dye used in the Gram 

 stain. 



Results of an attempt to reverse the Gram reaction are 

 described. 



There is described a modified Gram stain which, without the 

 use of mordants or alcohol, gives very good differentiation when 

 using many of the American dye products. 



RECOMMENDATIONS 



1. That the Comniittee on Pure Culture Study of the Society 

 of Bacteriologists mstead of attempting to select any one Gram 

 method to be used as the standard method in the study and 

 description of pure cultures designate the control organisms to 

 be used in checking up the stain. Any Gram method •jvhich 

 would give sharp differentiation between the two control organ- 

 isms could be considered a satisfactory Gram stain to be used 

 in the study of pure cultures. The selection of the control organ- 

 isms will require considerable study as the organisms selected 

 should have the same size and morphology when grown under 

 identical conditions and should require a first class stain to bring 

 out sharp differentiation. The custom of using staphylococcus 

 and typhoid as control organisms is not satisfactory. The 

 control organisms selected could be sent out to the different 



lOnSNAI. or BACnSBlOLOOT, VOL. Til, HO. 2 



