VARIATIONS IN TYPHOID BACILLI 305 



tions of 1 : 50 and 1 : 100 occurred, visible only with a lens. After 

 that not the sUghtest agglutination could be seen in any dilution 

 up to 1:50 until the forty-ninth day. On the forty-ninth day 

 shght agglutination was visible by lens up to 1:300 dilution, 

 and on the sixty-fourth day, we could recognize good agglutina- 

 tion in 1:50 dilution of serum. Then within about two weeks 

 it reached almost the highest dilution of the serum attained by 

 the control culture. Nine tests were made with the Rawlings 

 serum. On and after the twenty- third day, we tested its agglu- 

 tinability five times with C-51 serum as well as with the Rawling's 

 serum. Readings at the end of two hours showed no agglutina- 

 tion for the first four times but agglutination appeared in 1 : 100 

 dilution of the serum after the forty-fifth day. In twenty-four 

 hours' readings no agglutination appeared in 1 : 50 dilution of 

 serum until the twenty-seventh day while on the thirty-third 

 day, and after, it occurred in a serum dilution of 1 : 900. 



During the same period we tested the strain seven times with 

 antityphoid serum (no. 3). Two hour readings showed that no 

 agglutination appeared in 1 : 50 dilution of serum until the forty- 

 ninth day. On the sixty-fourth day good agglutination appeared 

 in 1:100 dilution. In twenty-four hours' readings until the 

 thirty-third day no agglutination was seen in 1:50 dilution. 

 From the thirty-seventh to the sixty-fourth day it always showed 

 agglutination up to 1 : 300 dilution of serum. 



Agglutinations of control cultures by each serum ranged from 

 1:8000 to 1:10,000. 



In all experiments done with different sera (Rawling's, C-188, 

 and Cohen) when we changed the serum media there was a shght 

 tendency toward agglutination in the first generation on the 

 new serum. After two or three generations in the new serum 

 media this tendency disappeared. 



II. We controlled our experiments with normal rabbit serum 

 broth in place of antityphoid serum broth media. Four parts 

 of broth and one part of normal rabbit serum (inactivated by 

 heating at 56°C. for half an hour) were used for this purpose and 

 a series of agglutination tests carried out with the same strains 

 and in the same manner as before. 



