REACTION OP THE HOST TO INFECTION 



223 



as it has been shown by Bordet that amboceptor does not unite 

 with complement in the absence of antigen. It seems more 

 probable that some other factor, such perhaps as a marked agglu- 

 tmation of the bacteria in the stronger solutions, may serve to pro- 

 tect them from the bacteriolytic action. 



Fixation of Complement.— As has been mentioned, it is pos- 

 sible to produce cytolysins for red blood cells. This is commonly 

 done by injecting the washed blood corpuscles of a sheep (o.i c.c. 

 + 0.5 c.c. salt solution) into a rabbit intravenously three or four 

 times at intervals of five days. The serum of the rabbit becomes 



Pig. 90.- 



-Illustratmg the conception of deviation of complement. 

 b, antigen; k, complement. 



a. Amboceptor; 



Strongly hemolytic for sheep's cells. The blood is drawn from 

 the carotid artery, the serum separated, rendered perfectly clear 

 and after heating to 56° C. for 30 minutes is stored in hermetically 

 sealed ampoules containing i c.c. each, in a low temperature 

 refrigerator. When this hemolytic amboceptor is diluted to the 

 proper point, which must be ascertained by trial and error, it 

 will just cause the complete hemolysis of a definite quantity of 

 washed sheep's corpuscles (0.2 c.c. of a 5 per cent suspension) 

 when combined with o.i c.c. of a 10 per cent solution of fresh 

 normal serum of guinea-pig (complement) . The mixture of this 

 quantity of the immune serum, which may now be called one unit 

 of hemolytic amboceptor, with 0.2 c.c. of freshly prepared 5 per 

 cent suspension of washed sheep's corpuscles produces a reagent 

 which setves for the detection of complement and the approxi- 



