98 DISSOCIATIVE ASPECTS OF BACTERIAL BEHAVIOR 



wright,' however, has presented certain exceptions. Of this fact we now have evidence 

 in members of the intestinal group, in B. siihtilis, B. proteus, and several other species. 

 Motility of a culture therefore loses all significance for species differentiation in sys- 

 tematic bacteriology, unless we can succeed in recoghizing the cyclostage with which 

 we are dealing. 



With reference to bacterial capsules, the same situation exists as for motility. So 

 far as we know at present, the capsule is the property of the organism of the S type, 

 the R form being destitute. With reference to the anthrax bacillus, which presents 

 certain other anomalies, the situation is not yet clear. The correlation is, however, 

 now recognized for B. coli, the pneumococcus, Friedlander's bacillus, M. tetragenus 

 and some Pasteurella forms. In none of these species does the presence or absenc.' 

 of capsules possess significance for systematic bacteriology unless we can recogniz.^ 

 the type of culture under examination. 



In addition to the foregoing, microbic dissociation manifests itself in important 

 biochemical and serological differences in the dissociated cultures; also, in a striking 

 manner with certain problems relating to virulence and immunity. These interesting 

 aspects of the subject cannot be discussed within the limits of the present con- 

 tribution.^ 



THE INCITANTS TO MICROBIC DISSOCIATION 

 AND THE PROBLEM OF REVERSION 



Although dissociative reactions must be regarded as occurring to some degree in 

 all bacterial cultures, probably beginning in the earliest hours of colony life, and al- 

 though in some cases they attain spontaneously such a magnitude that they attract 

 the notice of the alert investigator, fortunately, in the study of this phenomenon, we 

 are not dependent upon cultural material showing such spontaneous transformations. 

 The reaction may easily be "forced" as a result of bringing to bear on the young, grow- 

 ing culture certain extraneous influences; and the nature of these influences may be 

 diverse. 



Probably the first influence to attract attention was aging, as first pointed out by Firtsch 

 for the spirillum of Finkler-Prior in 1888. Most of Baerthlein's colony variations, as also 

 those of Eisenberg, were consequent to aging in broth or on agar, and to the use of alkaline 

 media. Under these conditions, one may often discover in the transition from the S to the R 

 forms the presence of the intermediate or transitional O, as clearly depicted by Firtsch, 

 Eisenberg, and many others. Other conditions of cultural growth favoring the reaction, with 

 the subsequent generation of the O or R forms of culture, include the following: changes in 

 temperature, various food substances, starvation, the physical state of the medium (solid 

 or liquid), the presence or absence of oxygen, the presence of antiseptic substances or dyes, 

 the reaction of the medium, the volume of the medium, microbic associations, passage through 

 animals, the influence of various kinds of normal animal blood or tissues, normal sera or 

 ascitic fluid, specific immune blood or sera, body excretions or secretions, and finall\' the 

 metabolic growth products of the same or other bacterial species. To these may be added 

 the influence of the bacteriophage which, in last analysis, is the reagent par excellence for 

 enforcing dissociation upon the sensitive, or even on the partially resistant, culture. Indeed, 

 only one other influence approaches it in degree or speed of action — and that is homologous 

 immune serum, as amply demonstrated by many experiments. 



' See Hadley, Philip: Joe. cit. ^ See chap, xlii 



