AGGLUTINATION 579 



bacterium, the organisms become agglutinated into clumps, this 

 phenomenon depending upon the presence of bodies in the 

 serum called agglutinins. 



It had already been found that the serum of convalescents 

 from typhoid fever could protect animals to a certain extent 

 against typhoid fever, and, in view of the facts experimentally 

 established, it appeared a natural proceeding to inquire whether 

 such serum possessed an agglutinative action and at what stage 

 of the disease it appeared. The result, obtained independ- 

 ently by Griinbaum and Widal, but first published by the latter, 

 was to show that the serum possessed this specific action shortly 

 after infection had taken place ; in other words, the develop- 

 ment of this variety, of anti-substance can be demonstrated at 

 an early stage of the disease. Agglutination may be said to be 

 observed generally in bacterial infections, though the degree of 

 the phenomenon and the facility with which it can be noted 

 vary greatly in different cases. Details will be found in the 

 chapters dealing with individual diseases, etc. Furthermore, the 

 phenomenon is not peculiar to bacteria ; it is seen, for example, 

 when an animal is injected with the red corpuscles of another 

 species, kcemagglutinins appearing in the serum, which have a 

 corresponding specificity. 



The physical changes on which agglutination depends cannot 

 as yet be said to be fully understood. It has been shown by 

 Nicolle and by Kruse that if an old bacterial culture be filtered 

 through porcelain, the addition of some of the corresponding 

 anti-serum produces a sort of granular precipitate in it ; and 

 that when minute inorganic particles are added to the mixture, 

 they become aggregated into clumps, as in the agglutination of 

 bacteria. The phenomenon would thus appear to be the result 

 of the interaction of the agglutinin and some substance in the 

 bacterial cell which is known as the agglutinable substance or 

 as the agglutinogen, the resulting effect being allied to precipita- 

 tion. Joos has found in the case of the typhoid bacillus that 

 there are two agglutinable substances which differ in their 

 resistance to heat — a and )8 agglutinogen, and that they give 

 rise to corresponding agglutinins. Further, as the result of a 

 comparative study of the agglutinins of a motile and a non- 

 motile variety of the hog cholera bacillus, Theobald Smith has 

 come to the conclusion that there is an agglutinin which is pro- 

 duced by and acts on the flagella, and another which is similarly 

 related to the bacterial bodies ; the former acts in very much 

 higher dilutions than the latter. Another factor necessary for 

 the phenomenon of agglutination is a proper salt content. Bordet 



