289 



THE RULE OF AGGLUTI:N^ATI0N IN IMMUNITY. 



By R. Greig Smith, D.Sc, Macleay Bacteriologist to the 



Society. 



When certain substances are introduced into the body-fluids of 

 animals, there are soon produced and found in the same fluids 

 bodies of an " anti-" nature. Speaking generally, it may be said 

 that these bodies act upon the substance originally introduced, 

 rendering it unfit to do harm to the animal. The manner in 

 which they do this depends largely upon the nature of the sub- 

 stance or substances which stimulated their production or called 

 them into being. An easily difi'usible toxin gives rise to an anti- 

 toxin which appears to neutralise the toxin much as a strong base 

 neutralises a weak acid. Organised cells are dissolved by specific 

 lysins, bacteria by bacteriolysins, red blood corpuscles by hsemo- 

 lysins, and so on. It is to the employment of these methods of 

 overcoming the attack of micro-organisms and their injurious 

 products that the condition of the animal which we term immu- 

 nity is due. But there are certain associated phenomena, the 

 significance of which is not clear and whose function in immunity 

 is not understood. One of these is the agglutination of bacteria 

 by specific and even non-specific agglutinins. The formation of 

 precipitates by specific precipitins is practically the same pheno- 

 menon, the difierence being that the precipitation occurs in the 

 absence of microbic cells. 



With regard to the mechanism of agglutination, I have shown"^ 

 that it could only be explained by the formation of a precipitate 

 (Kraus' precipitate) on the capsules and flagella of the bacteria, 

 and that it is really this precipitate or coating upon the cells 

 that is flocculated or agglutinated by the salts of the serum or 

 suspension. The bacteria are carried mechanically with the 



* These Proceedings, 1900, 75. 

 19 



