230 INFECTION AND RESISTANCE 



is evident most markedly in the cases of biologically related micro- 

 organisms like the typhoid, paratyphoid, and colon bacilli, this is not 

 necessarily the case, and in some instances the immunization of an 

 animal with a given bacterium may produce minor agglutinins for 

 other bacteria that have no morphologically or culturally demonstra- 

 ble biological relation to that which reacts with the major agglutinin. 

 We may obtain the most graphic survey of these conditions by exam- 

 ining one of a number of experimental protocols in which such major 

 and minor agglutinin formation is illustrated. Thus in the work of 

 Hiss 38 on the dysentery bacilli the following relations were ob- 

 served : 



A serum produced in rabbits by immunization with the Shiga 

 bacillus agglutinated the Shiga bacillus in dilutions of 1 to 20,000, 

 the "Baltimore," "Harris," "Gray," and "Wollstein" bacillus 1 to 

 1,200, the Y bacillus and others 1 to 200. 



An Anti-Y bacillus serum, which agglutinated this bacillus 1 to 

 6,400, agglutinated the Baltimore bacillus 1 to 1,600, and the Shiga 

 bacillus 1 to 100. 



Anti-"Baltimore" bacillus serum agglutinated this bacillus 1 to 

 3,200, and the Y bacillus 1 to 400, and the Shiga bacillus 1 to 100. 



In this series there is fair correspondence between cultural bio- 

 logical relations and agglutination, and from many such investi- 

 gations it would seem that "group" agglutination might be taken 

 to represent a method of determining biological classifications simi- 

 lar to the zoological relations revealed by the precipitin reaction. 

 While, in a general way, this is undoubtedly true, nevertheless great 

 caution must be exercised in relying upon such evidence for classifi- 

 cation, since notable exceptions have been observed. Park, 39 for 

 instance, cites a case in which a horse, immunized with a paradysen- 

 tery bacillus, agglutinated a colon strain in dilutions up to 1 to 

 10,000. Similarly Durham 40 found that two members of the colon 

 group one saccharose fermenting reacted almost identically with 

 the same agglutinating serum, while the agglutinations of two cul- 

 turally identical bacilli of the hog cholera group were entirely at 

 variance. 



The cause for the phenomenon of group agglutination must un- 

 questionably be sought in the nature of the bacterial agglutinogens, 

 and it is but reasonable to assume that living cells so little differen- 

 tiated biologically and morphologically should have much in common 

 chemically as well. The bacterial cell, moreover, may contain sev- 

 eral antigenic complexes and, beside its specifically peculiar constitu- 

 ents, therefore, we may suppose that every bacterium contains addi- 

 tional antigenic substances which it has in common with other 



38 Hiss. Jourri. of Med. Res., 13, N. S., Vol. 8, 1904. 



39 Park. "Pathogenic Micro-organisms," 1910, p. 166. 



40 Durham. Journ. of Med. Res., Vol. 5. 



