THE PHENOMENON OF AGGLUTINATION 243 



However this may be, and we must admit that explanations of 

 these phenomena are as yet largely speculative, a fact which interests 

 us particularly in connection with the phenomena under discussion 

 at present is the influence exerted upon the charge of bacteria by 

 exposure to the influence of serum. Bechold, 69 as well as Neisser 

 and Friedemann, 70 assert that bacteria which have absorbed ag- 

 glutinin no longer wander to the anode, but act as though they had 

 been deprived of electrical charge, and precipitate between the elec- 

 trodes. 



Bechold has suggested, for this reason, that it may be possible 

 that bacteria in the normal condition are protected from the action 

 of the electrolyte by a membrane or coating of protoplasm which 

 acts as a protective colloid. The absorption of agglutinin may alter 

 this in such a way that they become amenable to the flocculating 

 effects of the salt ions. In keeping with such an opinion is the well- 

 known observation of the inagglutinability of capsulated organisms, 

 which, as Pprges 71 has shown, become agglutinable as soon as the 

 capsules have been destroyed by heating in a weak acid. 



That the absorption of agglutinin indeed alters the electric sta- 

 bility of the emulsified bacteria further appears from the fact that 

 "agglutinin" bacteria 72 are agglutinated by concentrations of salts 

 which are too slight to affect the normal micro-organisms. In this 

 respect there is close similarity between the flocculation of agglutinin- 

 bacteria and such emulsions as kaolin and mastic, whereas bacteria 

 without agglutinin require much higher concentrations of the salts 

 to produce like effects. The absorption of agglutinin may have re- 

 moved a factor which protected the bacteria against the influence of 

 the salt. On the other hand, it is equally just to assume and this 

 is more likely and corresponds with Bordet's views that the ab- 

 sorption of agglutinin has "sensitized" the bacteria to the action of 

 the electrolyte. The experimental facts upon which the above state- 

 ments are formulated are largely found in the important papers of 

 Neisser and Friedemann whose work brought out, likewise, inter- 

 esting analogies of the colloidal precipitations with the phenomenon 

 which we have described above as the proagglutinoid zone. 



In regard to the greater amenability of agglutinin bacteria to 

 flocculation by electrolytes, the following protocol, adapted from the 

 work of these authors, will explain itself. They were tabulated from 

 experiments in which different quantities of normal y solution 

 of various salts were added, on the one hand to emulsions of unal- 



69 Bechold. "Die Kolloide in der Biologic u. Medizin," Steinkopf, Dres- 

 den, 1912. 



70 Neisser and Friedemann. Munch, med. Woch., Vol. 51, 1904, pp. 465 

 and 827. 



71 Forges. Ztschr. f. exp. Path. u. Therapie, 1905. 



72 "Agglutinin" bacteria bacteria which have absorbed specific agglutinin. 



