48 IMMUNITY 



A loose chemical union takes place between the bacteria and the 

 immune body, but no such union occurs between the complement 

 and the bacteria. The same chemical union occurs between the 

 red cells and the immune body in haemolysis, but not between the 

 cells and the complement. 



Ehrlich holds that there are many complements, each one different 

 from the other, and that their action is specific for the different kinds 

 of bacteria or cells with which an animal may be immunized. Bor- 

 det and Buchner, on the other hand, maintain that there is but one 

 complement. 



The solution of any cells by immune bodies, or anti-bodies, as 

 they have been called, is known as cytolysis. And cytolysins may 

 be produced by making anti-bodies of nerve cells, leucocytes, epithe- 

 lial cells, liver cells, as well as blood cells, by immunizing an animal 

 against these different cells with repeated injections of the cells or 

 emulsions of them. 



\_J^gglutinins are peculiar bodies which have the property of caus- 

 ing certain cells to agglutinate. One of the earliest manifestations 

 of immunity of a certain serum to bacteria, or to blood cells, is this 

 peculiar action of the serum causing either the bacteria or blood 

 cells to clump together in masses. Part of Pfeiffer's reaction is the 

 agglutination of the cholera spirilla in clumps before they are dis- 

 solved by the complement and immune body. 



If the serum of a typhoid fever patient is mixed, even in high dilu- 

 tions with some typhoid bacilli, the latter are clumped in isolated 

 groups. Clinically this is known as the Widal reaction, and is the 

 most reliable single sign of typhoid fever. 



These agglutinins may be produced artificially by injecting large 

 and increasing doses of bacteria into animals. After a time, in 

 the serum of the rabbit, there develops a peculiar body which 

 agglutinates typhoid bacilli, if they are brought in contact with it. 

 Sera can be rendered so highly agglutinative as to produce this 

 reaction even if diluted 100,000 times or more. 



If an animal is immunized against spermatozoa, or the red blood 



