JOHN W. CHURCHMAN 29 



other hand, thought gram positivity is solely dependent on the degree of dispersal of 

 the nucleo-proteins: in gram negatives the stained nucleoprotein forms a colloid of 

 high dispersion ; in gram positives it forms an emulsoid ; when gram positives become 

 negative the dispersion is increased. Deussen' concludes his exhaustive study of the 

 subject by stating that the gram reaction depends on the chemical nature of the cell 

 contents which undergo — according to their chemical structure — a greater or lesser 

 degree of hydrolytic splitting of the molecule. The reaction belongs in the complica- 

 ted field of nuclein combinations. It is chemical and not physical. 



It has been for a long time believed on the basis of statements attributed to Unna^ 

 that gram positivity depends on the formation of a peculiar iodine-dye-protein com- 

 pound and that only para-rosanilin dyes could be used for this purpose. That the 

 chemical process involved may not be quite so simple as this was shown by Eisenberg 

 who reported that the reaction could be produced with deeply colored dyes of the 

 acid class as well as with basic dyes and that the use of mordants is not necessary. 

 None the less, para-rosanilin dyes are the best for the purpose, and much the most 

 clear-cut results occur when mordants are used. 



Bacteria were for a long time treated as though their constitution were constant, 

 and characteristics were assigned to them which — by implication at least — they were 

 supposed to exhibit always and under all conditions. That they are, as a matter of 

 fact, biological units showing all the changes of metabolism, that they carry on res- 

 piratory processes, that they undergo dissociation, that they exhibit polymorphism — 

 these things are now well known. It is clear, therefore, that many of their character- 

 istics are constantly changing and that many of them may be made to change more or 

 less at will by alterations in the environment. Reversibility of the gram reaction by 

 acids (Deussen)^ and by coal-tar dyes (Churchman)^ has already been referred to; and 

 it must again be emphasized that the gram reaction of a given organism is constant 

 only when the conditions of examination are held constant. It must also be borne in 

 mind that gram positive organisms differ among themselves as to the stability of 

 their gram positivity. Neide,4 for example, used the term Gramdauer to indicate that 

 since a number of factors influenced decolorization by alcohol (among them the con- 

 centration and temperature of the alcohol used) gram positive organisms differed 

 among themselves as to the length of time they could retain stain when exposed to 

 decolorizers. Henrici^ showed that in yeast cells the cytoplasm is not homogeneous as 

 regards gram positivity, certain granules appearing in the decolorizing cell which hold 

 the dye longer than others. The author has recently made very clear the fact that not 

 all gram positive organisms are equally stable in their gram positivity.* Certain of 

 these organisms (e.g., M. freudenreichi) are extraordinarily stable in this respect; 

 others (e.g., B. anthracis), though equally gram positive, are less stable. Exposure of 



' Deussen, E. : loc. cit. 



'Unna, P. G.: Monatschr.f. prakt. Dermatol., Supplement No. 6. 1887. 



3 Churchman, J. W.: Stain Technology, 2, No. i. 1927. 



<Neide, E.: Centralbl.f. BakterioL, 35, 508. 1904. 



sHenrici, A. T.: /. Med. Research, 30, 409. 1914. 



^ Churchman, J. W.: Stain Technology, 2, No. i. 1927. 



