172 VICTOR BURKE 



pass readily through the cell membrane of the Gram positive 

 organisms owing to the size of the pores. It does not come within 

 the scope of this paper to give a critical analysis of the facts 

 bearing on the above theories. For further discussion the 

 reader is referred to a recent paper by Benians (1920) in which 

 the evidence in support of a physical explanation of the Gram 

 reaction is clearly presented. 



We wish to describe here the results of attempts to apply to 

 practical staining methods certain of the conceptions presented 

 in Dr. Benians' article. The results obtained have some bearing 

 on the questions involved and may stimulate others to further 

 research along similar lines. 



Benians divides bacteria into three groups as regards the 

 Gram reaction: (1) Gram positive organisms into which the 

 dye penetrates and from which the dye-iodine precipitate is 

 not readily washed out by the decolorizer; (2) Gram negative 

 organisms hke the gonococcus into which the dye penetrates 

 but from which the dye iodine precipitate is rapidly washed out 

 by the decolorizer; (3) Gram negative organism of the cohform 

 type into which the dye probably does not penetrate and under 

 certain conditions is not even absorbed into the surface of the 

 cell and which are therefore readily decolorized. 



According to the physical conception of the Gram reaction the 

 cell membrane of the Gram positive organism does not allow the 

 passage of the compound dye-iodine molecule when in solution 

 in the decolorizer. If the dye-iodine precipitate in solution in 

 the decolorizer can not pass out of the cell due to the character 

 of the cell wall then we are justified in assuming that under similar 

 conditions the dye-iodine precipitate can not pass into the Gram 

 positive cells. We can also reasonably assume that since the 

 dye-iodine precipitate readily passes outward through the wall 

 of Gram negative organisms like the gonococcus it will just as 

 readily pass inward through the cell wall in so far as physical 

 conditions operate. It follows then that if we expose films of 

 staphylococcus and gonococcus to an alcoholic solution of the 

 dye-iodine precipitate the dye-iodine compound should penetrate 

 the gonococci but not the staphylococci. Also since 75 per cent 



