TOHN H. NORTHROP AND PAUL H. DE KRUIF 



661 



TABLE IV. 



+ 4 +18 



^ +2 1 + 9 



t ol 



^ -4 g-18 



-6 S-e? 



-B -36 



-9 



^/2.56o ^40 Meo V40 



Dilation of immune serum 



Ho 



Fig. 4. Effect of immune serum on the potential and agglutination of Type 

 D and Type G at different pH. G. P. A. Buffer. 



The results are the same as with egg albumin. In every case the acid 

 agglutination zone is shifted to the alkaline side, and the amount of 

 serum required to agglutinate is a minimum near the isoelectric point 

 of the organism. This result had been noted by Krumwiede and 

 Pratt,' and by Michaelis and Davidsohn.'*' It is noticeable also that 



^ Krumwiede, C. K., Jr., and Pratt, J., Z. ImmunUatsforsch., Orig., 1913, 

 xvi,517. 



*° Michaelis, L., and Davidsohn, H., Biochcm. Z., 1912, .\lvii, 59. 



