SUMMARY AS TO ANTI-SERA. 447 



toneum, the normal bactericidal power of the peritoneal 

 fluid comes into action and completes the process. It would 

 be fruitless to discuss the nature of these reactions in greater 

 detail, as many of the important points are still sub judice. 

 It is sufficient to point out the dual character of the process 

 involved in the action of these antimicrobic sera, and the 

 fact that they contain substances which in very minute doses 

 become effective against the corresponding organisms. 



The observations just described are of great importance 

 in relation to the nature of acquired immunity, and further, 

 they have led to the discovery of the method of serum 

 diagnosis of disease, which has been applied especially to 

 typhoid fever, as already detailed (vide p. 322). It had 

 been already found that the serum of convalescents from 

 typhoid fever could protect animals to a certain extent 

 against typhoid fever, and, in view of the facts experiment- 

 ally established, it appeared a natural proceeding to inquire 

 whether such serum possessed an agglomerating action and 

 at what stage of the disease it appeared. The result, 

 obtained first by Widal, was to show that the serum possessed 

 this specific action long before the cure of the disease, in 

 fact shortly after infection had taken place. A process of 

 immunisation accordingly appears to be progressing from 

 an early stage of the disease. It has also been shown 

 recently by M'Fadyean, and also by Delepine, that the 

 glanders bacillus, which of course is a non-motile organism, 

 becomes agglomerated by the serum of animals suffering 

 from glanders. Bordet has found that on the contrary, 

 anti-streptococcic serum has no such action on a strepto- 

 coccus. The nature of this agglomerating action is not 

 yet fully understood. 



Summary with regard to Anti-Sera. In a former 

 chapter it has been shown that in the production of disease 

 by bacteria there are two main factors concerned, viz., the 

 multiplication of the living organisms in the tissues and 

 the production by them of toxines. The facts which have 

 been stated above show that in the blood serum of highly 

 immunised animals there are present substances of remark- 



