THE MECII.WISM OF ACI(lLrTI\\TfO\ 187 



Tlii.s indicates that the ap'g'hitinins cause a eliaii^e in tht- bacteria which 

 brings them under the same physical laws as the inorganic colloidal 

 suspensions, which are characterized by being precipitated by the 

 addition of traces of electrolytes.'^^ This precipitation is imdoubtedly 

 due to changes in solution tension and surface tension (see ''Precipi- 

 tation of Colloids," introductory chapter). Before the agglutinin 

 combines with the bacteria they behave like the colloidal solutions 

 of organic colloids, lieing precipitated only by the salts of heavy 

 inetals, alcohol, formalin, etc., or by great concentrations of neutral 

 salts. Field and Teague '^® have found that agglutinins carry positive 

 charges while bacteria are negative, and that by the electric current 

 agglutinins can be separated from bacteria with which they have com- 

 bined ; this shows that the agglutinin is not destroyed in the reaction. 

 Teague and Buxton ^^ consider that neutralization of the electric 

 charge of the bacteria is not, however, the only important factor in 

 agglutination. 



According to Bechhold ~^ normal bacteria behave like inorganic 

 suspensions that have each particle protected by an albumin-like 

 membrane, which prevents them from being thrown out of suspen- 

 sion by solutions of alkali salts, etc. After being acted on by agglu- 

 tinin they are so altered that they behave like the unprotected inor- 

 ganic suspensions, and are precipitated by salts and other electro- 

 lytes. This suggests the possibility that the agglutinin makes the 

 bacteria permeable for these electrolytes. Buxton and ShaflPer "^ also 

 found that bacteria which have been acted upon by agglutinin be- 

 have as if their proteins had been so changed that they are more 

 capable of absorbing or combining with salts than when in their nor- 

 mal condition. Strong salt solutions inhibit agglutination by prevent- 

 ing the binding of the agglutinin.^" Tulloch ^°^ observed that in the 

 presence of salts of mono- and di-valent cations, unsensitized bacteria 

 do not readily precipitate or agglutinate, but sensitized bacteria, as 

 Bordet show^ed, agglutinate with small quantities of salts. In this 

 respect unsensitized 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 difiPerent degrees of denatura- 



75 Arrheiiius (Zeit. physikal. Chem., in03 (46), 415) lias attempted to show 

 that the gas laws are applicable to tlie partition of afrslutinin between the bac- 

 teria and the medium, which he compares to tlie partition of iodin between water 

 and carbon disuli)hid. This idea is not accepted by Craw (loc. rit.). nor by 

 Dreyer and Douglas, Proc. TJoval Soc, 1910 (S2), 185. 



76, Jour. Exper. INFed., 1007 (0), SO. 



77 Zeit. physikal. Chem., 1007 (57). 70. 



78 Zeit. f. physikal. Chem., 1004 (48), .385. 



79 Zeit. physikal. Chem., 1007 (57), 47. 



80 Landsteiner and St. Welecki, Zeit. Immunitat., 1910 (8), 397. 

 80a Biochem. Jour.. 1014 (8), 203. 



