J 



60 IMMUNE SERA 



fore is not sufficient to cause a clumping to occur. 

 Naturally, the presence of salts does not alter the 

 condition, as the kations also carry a positive 

 charge. 



That the bacteria play a passive role in the phe- 

 nomenon of the agglutination is showr; by the fact 

 that non-motile organisms are agglutinated just 

 as well as motile organisms. This is evidenced 

 by the agglutination of glanders bacilli, the pneu- 

 mococci, etc., and also by the fact that dead bacteria 

 are specifically agglutinated. 



Group Agglutinins. For some time after their 

 discovery the agglutinins were regarded as strictly 

 specific, i.e., a serum derived, for example, from a 

 typhoid infection would agglutinate only typhoid 

 bacilli and no others. After a time, however, it was 

 found that such a serum would frequently aggluti- 

 nate somewhat related organisms, though not, 

 usually, to so high a degree. In other words, while 

 agglutinins may be nearly, if' not quite, specific in 

 their action, a serum which produces agglutination 

 may be far from being so. 



The following examples will illustrate the point.' 

 In a case of infection with paratyphoid bacilli, 

 type B, the bacilli of the infecting type B were 

 agglutinated i : 5 700 ; typhoid bacilli, however, only 

 1:120, while paratyphoid bacilli type A were not 

 agglutinated at all. In a case of typhoid infection 

 an agglutination with a dilution of i : 40 was obtained 



