MECHANISM OF BACTERIOLYSIS 



229 



treated with their specific immune body, continue to grow in the ordinary 

 way and have lost none of their pathogenic properties, but they differ from 

 non-sensitized organisms not only in their susceptibility to the action of the 

 thermolabile substance or complement- (vide infra) present in all normal 

 serums, but also in that they are more easily ingested and destroyed by 

 leucocytes. 



The immune body is known by different names, substance sensibilisatrice 

 (Bordet), fixateur, amboceptor (Ehrlich). Occasionally it is described as 



i c 



FIG. 159. Ehrlich's diagram to explain the interaction between the immune 

 body and complement. 



A, micro-organism or antigen ; /, immune body, sensibilisatrice, amboceptor, 

 flxateur or antibody ; C, complement, alexin or cytase. 



the antibody because it is antagonistic to the substances inoculated into 

 animals for the purpose of immunizing them. These latter substances are 

 therefore called antigens. Thus, in immunizing animals against the typhoid 

 bacillus the antigen is the typhoid bacillus and the antibody the new product 

 appearing in the serum in response to the inoculation of the antigen and 

 which has the property of attaching itself to the typhoid bacillus and so of 

 rendering the bacillus susceptible to bacteriolysis. 



B. Complement. The immune body prepares organisms for the action of 

 the substance contained in the serum of normal animals. This latter sub- 

 stance in conjunction with the immune body produces bacteriolysis, hence 

 the name complement by which it is generally described (Ehrlich). By some 

 authors, however, it is occasionally referred to as alexin (Bordet) or cytase 

 (Metchnikoff and Buchner). 



The complement is not a product of immunization and is not specific but 

 is present in all normal serums and is fixed indifferently by all organisms 

 through their specific immune body. 



When complement is mixed with micro-organisms it is only taken up by 

 them if they have been sensitized. Complement has no affinity for non- 



