VARIATIONS IN TYPHOID BACILLI 307 



This experiment showed that typhoid strains lose agglutin- 

 abihty in the same degree, whether cultivated in a serum broth 

 of their own specific immune seruna or on a serum immunized 

 against other strains. No difference was observed between 

 rapid xylose fermenters and slow xjdose fermenters. 



IV. The above experiments were performed with old stock 

 cultures. We next repeated these tests using freshly isolated 

 strains. Two strains (Owen and Boyle) which were obtained 

 from typhoid carriers' stools were used after thi'ee generations 

 on artificial media. 



The media consisted of four parts of broth and one part of 

 Rawling's or C-51 serum, the agglutinating titre being 1 : 15,000. 



The Owen strain was cultivated in Rawling's serum and C-51 

 serum broth and transplanted into fresh media six times in seven 

 days. It reached its maximum inagglutinability (1:900) in 

 seven days with the same serum in which it was grown. When 

 tested with the other serum its loss of agglutinability was not 

 so great. A few days later both cultures in Rawling's serum 

 broth and in C-51 serum broth recovered their agglutinabihty. 



Observations were made with the Boyle strain in the same 

 manner as with the Owen strain. In this case the maximum 

 point of inagglutinability in Rawling's serum broth and in C-51 

 serum broth was reached on the fourth day. 



On carrying out agglutination tests with Rawling's serum one 

 strain (Rawling's serum culture) continued its inagglutinability 

 (1:300) at least ten days, while the other culture in C-51 serum 

 broth regained its agglutinability on the seventh day. The 

 other tests with C-51 serum ran almost parallel. The maximum 

 point of inagglutinabiUty (1:900) was reached on the fourth 

 day and agglutinability was recovered on the seventh day. 



In the foregoing experiments observations were made concern- 

 ing the character of the growth of typhoid bacilli in serum broth 

 in vitro. During the first few days the bacteria grew like a 

 mass of cotton at the bottom of the tubes; later when the bacteria 

 had partly recovered agglutinability some organisms grew on 

 the surface of the media, forming a film, as well as at the bottom. 

 Up to this point the mass of bacteria is not easily broken up by 

 shaking, but after recovery of agglutinability it becomes very 



