150 CHEMISTRY OF IMMUNITY AGAINST BACTERIA 



agglutinogens is still a matter of dispute. 1 Likewise, the ques- 

 tioD as to whether they occur in the membrane or within the 

 bacterial cell is still open, but Craw 2 found that the insoluble 

 residue of crushed typhoid bacilli, after being washed free of all 

 soluble constituents, was but slightly agglutinated by active 

 serum ; therefore, the agglutinogeus are probably soluble intra- 

 cellular substances. 



Agglutinated bacteria can be again separated from one 

 another by the action of organic and inorganic acids, alkalies, 

 acid salts, and by heating to 70 or 75, and after once being sep- 

 arated they cannot be reagglutinated by fresh serum. 3 



The Mechanism of Agglutination. This has been a 

 fruitful field of research, in which the application of physical 

 chemistry has been very profitable. At first it was believed 

 that the clumping was brought about by loss of motility, until 

 it was found that non-motile bacilli were equally affected. Sim- 

 ilarly, the hypothesis of adhesion of the flagellse was disposed 

 of. Gruber 4 and others supposed that a sticky substance, " glab- 

 rificin," was absorbed from the serum by the bacilli, which 

 caused them to adhere on contact with one another ; but this 

 does not explain the nocking together of non-motile bacilli. 

 Paltauf considered that the specific precipitin (see next section) 

 produced by immunization carried the bacilli down in the pre- 

 cipitate formed, and there is reason to believe that this reaction 

 is of importance, but it does not explain all the facts of agglu- 

 tination, nor is the relation between agglutinating and precipi- 

 tating power of immune serums a constant one. Neisser and 

 Friedmann 5 found that if the bacterial cells were saturated with 

 lead acetate, washed in water until all soluble lead was removed, 

 and then treated with H 2 S, they were promptly agglutinated 

 and precipitated, supporting other observations that indicate 

 that precipitation within the bacterial cells can lead to agglu- 

 tination. This sort of agglutination is probably related to the 

 process of formation of coarse flocculi in solutions, and probably 

 depends upon alterations in surface tension. 



Bordet 6 made the important observation that agglutination 

 would not occur if both the bacterial suspension and the agglu- 

 tinating serum were dialyzed free from salts before mixing ; but 

 if, to such mixtures, a small amount of NaCl was added, agglu- 



1 See Paltauf, Kolle and Wassermann's Handbuch, Bd. 4, p. 726. 



2 Loc. cit. , infra. 



3 Eisenberg and Volk, Zeit. f. Infektionskr., 1902 (40), 192. 



4 For complete bibliography, see Craw. Jour, of Hygiene, 1905 (5), 113. 



5 Munch, med. Woch., 1904 (51), 465 and 827. 



6 Ann. d. 1' Inst. Pasteur, 1899 (13), 225. 



