320 



COLLECTED STUDIES IN IMMUNITY. 



proagglutinoid from the agglutinin could only be answered by showing 

 that the amount of proagglutinoid already present in this serum could 

 be increased by heating, by continued exposure to light, or by the 

 addition of chloroform. See Table V. 



TABLE V. 



The development of the proagglutinoid from the agglutinin was 

 still more distinct in a fresh typhoid immune serum (goat). This 

 serum, which had shown no zone of proagglutinoid, showed a dis- 

 tinct zone after being heated twice to 60 for four hours. 



By this experiment the higher affinity of the proagglutinoid is 

 already demonstrated. It can, however, be confirmed by other 

 experiments. By shaking the dysentery serum with chloroform, it 

 was possible to effect almost a complete transformation of agglutinin 

 into proagglutinoid so that the serum hardly agglutinated in any 

 dilution. When to a dose of the unchanged dysentery serum, suffi- 

 cient by itself to effect agglutination, I added decreasing amounts 

 of the serum treated with chloroform, no agglutination was obtained 

 in the dilutions up to 1:160. (Control tests with chloroformed 

 normal serum were invariably made.) The same result could be 

 obtained with dysentery serum that had been heated. Dysentery 

 serum heated for 3 hours to 65 C. was able in dilutions of 1 : 10 to 

 1:320 to prevent agglutination by such a dose of the unchanged 

 dysentery serum which by itself would have sufficed to agglutinate 

 1 : 160. (See Table VI.) 



Finally it remained to prove that the proagglutinoid had really- 

 been anchored by the bacteria, i.e., that the agglutinable group of 

 the bacilli had been blocked. This was readily accomplished by 



