76 THE MECHANISM OF AGGLUTINATION, 



up. It is clear that the loss of motility or suspension of vitality 

 is a necessary factor in the phenomenon. 



The action of the serum upon the bacteria has been variously 

 explained. Pfeiffer saw the bacteria swell just as they did in the 

 peritoneal fluids of immune animals, and Gruber (2) considered 

 this to be the cause of agglutination, the outer membranes of the 

 bacteria becoming gelatinous and sticking to one another. 



Kraus (3) obtained a precipitate on adding anti-cholera scrum 

 tn a filtered culture of cholera vibrions. This is an agglutination 

 of the soluble products of the metabolism or of the disintegration 

 of the bacteria. Nicolle (4) showed that these agglutinable sub 

 stances were excreted by the bacteria during life as well as being 

 contained in the products of their disintegration. These bodies 

 are not affected by a temperature of 150° C. When inert chemical 

 substances such as talc, or as Nicolle showed, foreign bacteria are 

 introduced into the filtured culture they are entrapped in the 

 precipitate produced by the active serum and appear to agglu- 

 tinate. Nicolle and also Paltauf considered that this gelatinous 

 precipitate surrounded the bacteria and caused them to adhere 

 together. Dineur considered that the precipitation took place on 

 the flagella, which becoming adhesive caused an entanglement of 

 the bacteria. 



In reviewing these hypotheses Bordet (5) considered that even 

 if the membranes were altered there was no reason adduced for 

 the bacteria becoming attracted to one another. He considered 

 that Kraus' precipitate was too slowly formed to account for the 

 rapid agglutination of the bacteria, and furthermore that the 

 coagulum upon the surface of the bacteria was only an idea and 

 had not been demonstrated. Bordet's objections seem to be 

 rather weak, for it is a well known fact that substances about to 

 separate out from a liquid do so rapidly when small particles are 

 present in the liquid, and there is every probability that there 

 will be a film of the precipitated substance upon the flagella and 

 upon the surfaces of the bacteria long before a precipitate becomes 

 visible in the Huid. 



