52 IMMUNITY 



Bacteria +inimune body + complement = solution (Pfeiffer's 

 reaction). 



Bacteria + immune body + complement (heated) = no solu- 

 tion. 



Bacteria + immune body (heated) + complement = solution. 



The same phenomena have been observed in the blood of 

 animals immunized against the red blood corpuscles of another 

 animal of foreign species. 



If a rabbit is immunized with the blood of a dog by repeated 

 and increasing doses, the serum of that rabbit will become h&mo- 

 lytic to the corpuscles of the dog's blood if they are mixed, pro- 

 vided some normal rabbit's blood complement is added to the 

 mixture. 



Dog's erythrocytes + immune rabbit serum = no solution. 

 Dog's erythrocytes + immune rabbit serum + complement = 

 solution. 



Dog's erythrocytes + immune rabbit serum + complement, 

 heated = no solution. 



The immune body acts as a preparer of the corpuscles, or 

 bacteria, so that the complement can act upon the cells. The 

 reaction is very like the action of pepsin on fibrin. Hydrochloric 

 acid must be present. 



(1) Pepsin + fibrin = no solution or lysis. 



(2) HC1 + fibrin = no solution or lysis. 



(3) Pepsin + HC1 + fibrin = solution or lysis. 

 The HC1 corresponds to the immune body. 



In the case of haemolysis, or bacteriolysis the action of the im- 

 mune body is specific. The immune body of cholera spirilla will 

 not prepare, or fix typhoid bacilli, so that they can be acted upon by 

 the complement. Nor will the immune body of dog's erythrocytes 

 prepare those of a pig, so that the complement may act on themu 



A loose chemical union takes place between the bacteria and 

 the immune body, but no such union occurs between the comple- 



