VARIATION OF SALMONELLA PULLORUM 51 



These results conclusively show that the variant VII I-a does not possess the 

 power to stimulate agglutinin production in the living natural host to the extent 

 that its parent strain does. Also, it failed to establish itself in the natural host. 



The absorptive capacities of several normal strains and their variants were 

 determined. In preliminary studies natural, positive pullorum serum and a 

 homologous chicken serum for Strain VIII were employed. Strain VIII and its 

 variant VI 1 1 -a were used for the absorbing organisms. The unabsorbed and 

 absorbed sera were tested with known pullorum antigen and with antigen pre- 

 pared for Strain VIII. The results in Table 19 show that the typical strain, VIII, 

 was capable of absorbing all of the agglutinins from its homologous serum and 

 from the natural serum, while variant VHI-a reduced the titre to a lesser degree. 



Table 19. — Results of agglutinin absorption. 



In the determination of the absorptive capacities of the different parent strain 

 and their variants, five sera which varied in titre were employed. The sera wer ' 

 tested with a stock antigen before and after absorption to determine the reduction 

 in titre. The absorbing antigens were prepared from either a 24- or 48-hour 

 growth, depending upon the yield obtained. The different sera were absorbed 

 with a live antigen which had a turbidity equal to tube 8 of McFarland's nephe- 

 lometer. However, in some cases a less dense suspension was found satisfactory to 

 bring about complete absorption. Some sera were absorbed three times, others 

 twice, depending upon the agglutinin titre and the absorbing power of the strain. 

 The serum and antigen dilution employed during absorption was 1:10. Twelve 

 original parent strains (I, II, III, VI, VIII, IX, XII, XIII, XIV, XVI, XVIII, 

 and I (Experiment I)) and 16 variants (I-a, Il-a, Ill-a, Vl-a, Vlll-a, IX-a, 

 IX-b, XH-a, Xll-b, XHI-a, XVI-a, XVIII-a, A, A-l, C and E, and four mis- 

 cellaneous strains) were studied. Since the results in general are very much the 

 same in the two groups (parent and variant) only one set of data is presented in 

 Table 20. It may be seen in the table that the variant does not possess the ab- 

 sorptive capacity of its parent strain. 



