VARIATIONS IN TYPHOID BACILLI 321 



definite character occurring in higher plants should not be 

 introduced into bacteriology; for the bacteriologist, who studies 

 his species not only from the morphological point of view, but 

 also with regard to biochemical and immunological reactions, 

 and who observes not a few generations only, but hundreds 

 and thousands of generations, would almost surely have to modify 

 the conception of the term in such a manner as to cause confusion 

 to the botanist. It, therefore, seems advisable to leave the term 

 mutation to the botanists and, for the present at least, to speak 

 of atypical varieties of bacteria or simply of variants. 



Typhoid bacilli grown upon normal serum do not become 

 inagglutinable. Cultivated continuously upon specific immune 

 serum they at first become inagglutinable, but if such cultivation 

 is persisted in for two weeks longer, eventually these strains 

 again become agglutinable. In some cases this return to normal 

 agglutinabihty does not occur until the seventy-second day. 

 This, however, is exceptional. It is important to notice that, 

 w^hereas in other experiments the normal characteristics had 

 developed, in this case a return to normal reaction with serum 

 was brought about in spite of a continuous subjection to the 

 unusual environment. 



Inagglutinability of the typhoid bacillus is accompanied by 

 inabihty to absorb agglutinin. There is no difference whatever 

 in these relations between the xylose slow and xylose rapid 

 fermenters. Our experiments do not indicate that capsular 

 material is concerned in the inagglutinabihty. Treatment by 

 the Porges method does not render the inagglutinable strains 

 agglutinable. 



Acid agglutination experiments by the method of Michaelis 

 showed that the inagglutinable serum strain reacted negatively 

 in the increasing concentrations of acetic acid, being in this 

 way similar to colon bacilh, whereas the same strain cultivated 

 in broth reacted with the acid typically as did MichaeUs typhoid 

 cultures. In other words, the inagglutinable strains showed a 

 changed reaction in regard to hydrogen ion concentration of the 

 environment. 



