THE MECHANISM OF AGGLUTINATION. 163 



Conclusions. 



I. Theories that explain bacterial agglutination by a swelling 

 and viscosity either of the membranes or cilia of the bacteria meet 

 with numerous objections and do not serve to explain all the phe- 

 nomena of agglutination. The theory that regards the forma- 

 tion of a precipitate in the fluid as the cause of agglutination is open 

 to the same objections. 



II. Agglutination may affect such different elements as red 

 blood corpuscles, bacteria, and casein. In all these instances of 

 agglutination by serum the same explanation must be accepted. 



III. We may conclude that the agglutinins by uniting with the 

 agglutinable substances lead to changes in molecular attraction 

 between the elements affected, either as among themselves or as 

 between them and the surrounding fluid. The entire phenomenon 

 of agglutination should be divided into two phases, of which the 

 first may be experimentally produced without the second. The 

 first is a period during which the isolated elements are affected by 

 the agglutinin, and the second a period of agglutination, properly 

 speaking. The individuality of the elements affected counts only 

 in the first phase. During the second phase, cells in obedience to 

 molecular attraction show, in their agglutination, only such pecul- 

 iarities as occur in the clumping of mineral particles. 



IV. The phenomena of agglutination resemble the phenomena 

 of coagulation very closely. 



V. The phenomena of true agglutination may be brought 

 about in limpid fluids in which the particles are extremely finely 

 divided. 



VI. Active sera may be compared with digestive juices in respect 

 to their coagulating and dissolving properties. It would seem as 

 if immunity would come to be regarded more and more from a 

 chemical standpoint as an instance of the physiology of digestion. 



VII. As was previously stated in an article on sera active against 

 blood corpuscles, the production of bacteriolytic substances in 

 animals during the course of vaccination cannot be regarded tele- 

 ologically. The animal body does not form these harmful sub- 



