204 AGGLUTINATION 



bacilli in a dilution of 1: 1,000; or a typhoid serum may act in like 

 dilution on a paratyphoid bacillus. In making a clinical diagnosis such 

 a mistake would be of little or no importance, but in the identification 

 of a bacterium it would be important. According to Paltauf the fol- 

 lowing dilutions are necessary for the positive identification of the 

 named bacteria: plague bacillus, 1: 1,000; typhoid and cholera bacilli, 

 1 : 10,000. The active substance in the serum, the agglutinin, is 

 undoubtedly a globulin. It is inactivated at temperatures which range 

 from 75 to 90 C. in different sera. 



The active constituent of the culture, the agglutinable substance, 

 is not, in my opinion, an essential constituent of the bacterial cells, 

 but consists of one or more proteins closely associated with the bac- 

 terial cells. It may be a protein already split off from the bacterial 

 pabulum in the culture medium preparatory to absorption, or it may 

 be an excretory product. The reasons for this belief may be briefly 

 stated as follows: 



1. Agglutination does not destroy the viability or virulence of 

 bacteria; therefore, the reaction does not disrupt the living bacterial 

 cell. 



2. Thoroughly washed typhoid bacilli are not agglutinable. 



3. When typhoid bacilli are thoroughly shaken in salt solution so 

 as to remove the flagellae and the bacilli are deposited in a centrifuge, 

 the emulsion of flagellae is agglutinable. 



4. Cholera bacilli, as shown by Neufeld, when shaken with 1 per 

 cent, alkali, which does not dissolve the cells but washes away the 

 adherent matter, the cleansed cells are not inagglutinable, but when 

 injected into animals they produce no agglutinin. 



Agglutination and precipitation are like phenomena. When a 

 bacterial culture is filtered, some of the proteins adherent to the bac- 

 terial cells pass into solution and constitute the precipitinogen, some 

 of the same class of near-cell proteins remain in close connection with 

 the cells and constitute the agglutinable substance or the agglutinogen. 

 Inorganic salts are essential to agglutination. The reaction is that of 

 a colloid and the specificity is due to the chemical structure of the 

 proteins entering into the reaction. The agglutinable substance is 



