BY R. GREIG SMITH. 77 



Bordet considers that the cause of agglutination is also the 

 cause of the coagulation of casein, of the precipitation of 

 chemical substances and of the agglutination of blood corpuscles. 

 To disprove Gruber's hypothesis that the swelling of the bacterial 

 capsule causes agglutination, he added a small quantity of an 

 active serum to a suspension of cholera vibrions in normal saline. 

 The clumps which formed were separated from the normal saline 

 by centrifuging and subsequent treatment with water. The 

 bacteria were shaken with the water until a homogeneous suspen- 

 sion was obtained. This was divided into two portions, to one 

 of which common salt solution was added and to the other dis- 

 tilled water. Clumping occurred in the former case, but not in 

 the latter. That common salt should cause the agglutination of 

 the immobilised bacteria shows that a swelling of the membranes, 

 if such occur, is not a necessary factor in the phenomenon. It is 

 contended by Bordet that the agglutination of bacteria by active 

 sera is identical in principle with the coagulation of casein by 

 rennet. In the furtherance of this idea he found that the serum 

 of animals inoculated with milk contained an enzyme that 

 coagulated milk after the manner of rennet. Since both pheno- 

 mena appear to be similar, he considered that the name agglu- 

 tination should be changed to coagulation, and the agglutinin's, 

 of which there are many varieties — each capable of clumping its 

 particular organisms — should be called coagulines. The agglu- 

 tinins he believes to be enzymes, an opinion which is shared }yy 

 Emmerich and Low (6). The mechanism of the process, as 

 explained by Bordet, consists primarily in the enzyme altering 

 the relations between the bacteria and the solution, and secondly, 

 as a result of the alteration the bacteria gather themselves into 

 clumps. 



It is claimed by those who have experimented with the 

 mechanism of agglutination that clumping is caused by a pre- 

 cipitate forming on the organisms (Nicolle, Paltauf ] and making 

 them adhesive, by the organisms swelling (Gruber), or by the 

 agglutinating enzyme causingthem to flocculate (Bordet). Neither 

 the formation of a precipitate on the bacteria, as Bordet has 



