78 THE MECHANISM OF AGGLUTINATION, 



pointed out, nor the swelling of the organism explains the reason 

 of their gathering together. With regard to the action of the 

 enzyme in causing them to run together, Bordet has shown that 

 once the bacteria have been acted upon by the active serum they 

 are flocculated by common salt. It has been shown in my former 

 paper that bacteria are not flocculated by common salt, from 

 which it is to be concluded that the organisms have through the 

 action of the active serum become altered into or have been 

 endowed with some substance that is capable of being coagulated 

 or flocculated. That it is not the action of the enzyme purely, is 

 shown by Bordet's experiment, but as I shall show he has wrongly 

 interpreted the phenomenon. He undoubtedly considers agglu- 

 tination to be the work of the enzyme alone and confirms it by the 

 action of rennet on milk, apparently forgetting that rennet does 

 not coagulate casein in the absence of salts of lime. The casein 

 is altered by the rennin into paracasein and an albumose, but 

 the paracasein is only coagulated in the presence of lime. 



The question then arises, what is the action of the active 

 serum 'I It is apparently not a coagulation of the protoplasmic 

 albuminoids, since bacteria, the albumen of which has been 

 coagulated by heat, are, as I have found, not flocculated by salts. 

 The immobilisation would seem to indicate an alteration of the 

 protoplasm. But since bacteria killed by heat are not flocculated, 

 it does not seem probable that any alteration which the protoplasm 

 might undergo would induce agglutination. We must therefore 

 look to an agglutinable substance being formed on the bacteria. 

 Since Kraus' precipitate is formed by the active serum sooner or 

 later in the fluid in which the bacteria have been grown, there 

 can be no doubt that the bacteria are saturated with the pre- 

 cipitable substance before it diffuses into the fluid. The pre- 

 cipitate would naturally form upon or in the bacteria very much 

 sooner than in the medium. It would appear first upon the 

 delicate flagella, which in their motion would strike one another 

 and on doing so would adhere. The motility would accordingly 

 cease, and the precipitate, having by this time formed on the 

 body of the organism, would be flocculated by the salts of the 



