146 LECTURES ON IMMUNITY 



compound is a highly dissociable one. For otherwise the 

 oft-observed washing out of the agglutinin from this com- 

 pound in the bacterium would be inexplicable. And, fur- 

 thermore, the absorption of the agglutinin ought to be 

 total until saturation was obtained, and thereafter only a 

 very slight increase (due to the physical absorption) ought 

 to be observed. 



But even if we suppose the compound to be dissociable 

 to a high degree, we might expect that the bound fraction 

 of agglutinin (C) should increase to a limit value with in- 

 creasing concentration of B (and T). As Eisenberg and 

 Volk remark, no such limit can be observed in the results 

 of their experiments. Even the assumption that the 

 agglutinin contains many different kinds of " agglutinin " of 

 different combining powers does not extricate us from 

 this difficulty. 



In favour of the hypothesis that the agglutination is the 

 consequence of a chemical combination, Joos has adduced 

 some experiments on the effect of partial additions of 

 agglutinin to a suspension of typhoid bacilli. He deter- 

 mined the least dosage of agglutinin that is able to agglu- 

 tinate all the bacteria in the test. Then he added a part 

 of this quantity to a similar suspension ; the agglutination 

 was incomplete. He centrifugated the solution and in this 

 way segregated the agglutinised bacteria and removed 

 them. Then he added a new portion of agglutinin to the 

 solution, and so forth, until all the bacteria had been agglu- 

 tinated. The total quantity of agglutinin added in the 

 several fractions in this manner was found to be equal to 

 the quantity necessary to agglutinate all the bacteria when 

 added at once. Considering the great experimental errors 



