16 



MASS. EXPERIMENT STATION BULLETIN 319 



of cells observed in 0.11 per cent saline solution in the absence of serum. One 

 antigen, No. 6, settled out in this salt concentration after negative serum was 

 added, but then only in the lower serum dilutions. Antigens 6, 7, and 8 exhibited 

 no clumping in the lower saline concentrations in the presence of positive serum, 

 while in the higher saline concentrations fine clumps were visible. However, 

 this clumping of cells was observed only in the first two serum dilutions. In the 

 higher dilutions the cells had settled out and appeared similar to the antigen 

 control. With antigen 7 definite clumping was observed in the first two dilutions, 

 no clumping or settling in the four succeeding dilutions, but slight settling in the 

 last and partial settling in the antigen control. It is evident that antigens 6, 7, 

 and 8 were highly sensitive to salt and practically inagglutinable in the saline 

 concentrations employed. Antigens 2, 4, 5, and 13 exhibited typical agglutination 

 in the 0.9 per cent saline solution and remained in suspension in the presence of 

 negative serum and in the antigen control. However, in the weaker salt concen- 

 trations the clumping of cells was not as marked and well defined as in a stronger 

 concentration. Also the titre was reduced with the weaker saline concentration. 

 It was also observed that the clumps in the lower dilutions were as a rule larger 

 than in the higher dilutions. Furthermore, in some instances the suspension 

 appeared more turbid after agitation in the lower dilutions than in the higher 

 dilutions and in the antigen control. This indicated that other substances aside 

 from the bacteria or bacterial fragments had precipitated. This phenomenon was 

 observed even after the H-ion concentration was lowered to pH 8.4 — 8.6. 



Table 3. — Reactions of variants with positive and negative pullorum sera 



IN DIFFERENT CONCENTRATIONS OF NaCI. 



