326 METHODS OF IDENTIFICATION AND STUDY 



matter introduced into the blood or tissues; but by 

 itself is a comparatively inert body, and is only capable 

 of exerting its maximum lytic effect in the presence of 

 and in combination with a specific antibody, or immune 

 body. 



Complement is obtained (unmixed with antibody) by 

 collecting fresh blood serum from any healthy normal 

 (that is uninoculated) animal. Guinea-pigs' serum is 

 that most frequently employed for experimental work. 



H&molysin (immune body, copula, sensitising body, 

 amboceptor) is a thermostable antibody formed in 

 response to the injection of red cells which although 

 in itself inert is capable of linking up complement 

 present in the normal serum to the red cells of the 

 variety used as antigen a combination resulting in 

 haemolysis. 



Haemolysin is obtained by collecting fresh blood serum 

 from a suitably inoculated animal and exposing it to a 

 temperature of 56 C. (to destroy the thermo-labile 

 complement) for 15 to 30 minutes before use. It is 

 then referred to as inactivated, and is reactivated by 

 the addition of fresh normal serum that is serum 

 containing complement. 



Haemolysin is of importance academically owing to 

 the fact that many of the problems of immunity have 

 been elucidated by its aid; but its present practical 

 importance lies in the application of the hcemolytic 

 system (that is haemolysin, corresponding erythrocyte 

 solution and complement) to certain laboratory 

 methods having for their object either ^the identifi- 

 cation of the infective entity or the diagnosis of the 

 existence of infection. 



For use in these laboratory methods of diagnosis it is 

 most convenient to prepare haemolytic serum specific for 

 human blood whether the laboratory is isolated or 

 attached to a large hospital. Ox blood, sheep blood or 

 goat blood if readily obtainable, may however be used 



