182 CHEMISTRY OF THE IMMUNITY REACTIONS 



permeable for these electrolytes. Buxton and Shaffer^** also found 

 that bacteria which have been acted upon by agglutinin behave as 

 if their proteins had been so changed that they are more capable of 

 absorbing or combining with salts than when in their normal condition. 

 Strong salt solutions inhibit agglutination by preventing the binding 

 of the agglutinin.-^ Tulloch^" observed that in the presence of salts 

 of mono- and di-valent cations, unsensitiz.ed bacteria do not readily 

 precipitate or agglutinate, but sensitized bacteria, as Bordet showed, 

 agglutinate with small quantities of salts. In this respect unsensit- 

 ized bacteria behave like "non-rigid colloids, " such as fresh egg white, 

 while sensitized bacteria resemble "rigid colloids," such as denatured 

 egg white. Hence he advances the hypothesis that the process of 

 sensitization is akin to that of denaturation of proteins, the specificity 

 perhaps depending on different degrees of denaturation. Mansfeld^^ 

 would bring agglutination into line with other serological reactions as 

 a protein digestion process, by his hypothesis that bacteria are held 

 in suspension by protective colloids which are digested by an enzyme, 

 the agglutinin. He finds in favor of this hypothesis that the tempera- 

 ture and reaction curves correspond to enzyme actions, that agglu- 

 tinating serum contains an enzyme digesting protein extracted from 

 bacteria, and that during agglutination the agglutinogen is destroyed. 



Agglutination obeys the same laws as other similar physical 

 phenomena; the rate of agglutination depends upon the concentration 

 of the suspension and of the electrolytes, and varies with the valence 

 of the cations. Although bacteria in an electric stream move toward 

 the anode like all suspensions, after being acted on by agglutinin they 

 are agglutinated by the current between the poles ;^2 this indicates 

 the importance of the electrical charges of the bacterial surfaces in 

 their agglutination reactions. 



In all respects the behavior of bacteria and agglutinin resembles 

 the behavior of colloidal mixtures in suspension (Neisser and Friede- 

 mann)'*'' which form an electrically amphoteric colloidal suspension, 

 so that the ions of electrolytes or the electric currents, by discharging 

 them unequally, cause precipitation. Physico-chemical researches, 

 however, have yet failed to explain the specific character of the ag- 

 glutinins for specific bacteria, but Michaelis^'* has developed an inter- 

 esting analogy in the specific agglutination of bacteria by acids. This 



28 Zeit. pliy.sikal. Chem., 1907 (57), 47. 



29 Landstoinor and Ht. VVclocki, Zoit. Iiuiiiunitiit., 1910 (8), 397. 

 5" Biocheni. Jour., 1914 (8), 293. 



3' Zeit. Iiiununitut., 1918 (27), 197. 



" Bocliliold; liowover, liuxton and Teague (Kolloid Zcitschr., 1908, II, Suppl. 

 2) 8tat(! tliat agglutinin bacteria do move towards tlie anode, but slower tli.'in 

 normal bat-teria. 



" Miincli. med. Woch., 1904 (51), 405 and 827; see also ( uranl-Mangin and 

 llemi, (.'onipt. Rend. Soc. I'iol., 1904, vol. 5(); ami Zangger, Cent. f. Hakt. (ref.), 

 1905 (3()), 225. 



^* Folia Serologica, 1911 (7), 1010; akso IJeniasch, Zeit. Iiumunitat., 1912 (12), 

 208. 



