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Scientific Proceedings (32). 



by means of complement fixation may or may not be successful 

 according to whether or not appropriate amounts of hemolytic 

 amboceptor and complement are employed. A large excess of 

 either one of these two reagents can prevent the test from reveal- 

 ing the presence of the antibody. While it is easy for a serologist 

 to see why complement should be used in definite and uniform 

 quantity, not every worker seems to be conscious of the disturbing 

 effects which are exerted by an excess of the amboceptor. In 

 view of the overlooking of certain principles of hemolysis by most 

 of the investigators of the present time a brief consideration of 

 this particular subject seems to be advisable. For the sake of con- 

 venience I take the example of the antisheep hemolytic amboceptor 

 for illustrating the influence of an excessive amount of the ambo- 

 ceptor upon the phenomenon of complement fixation. The effects 

 exerted by the excessive sensitization is two-fold. The first effect 

 is to augment gradually the activity of guinea-pig's complement 

 by increasing doses of the amboceptor, until a maximum is 

 reached. Thus in the presence of one unit of amboceptor o. l 

 c.c. of the complement is usually required to produce complete 

 hemolysis. By using four, eight and twenty units of the ambo- 

 ceptor the same effect is obtainable with ^, ^ and yL of the o. l c.c. 

 of complement respectively. For this reason it is impossible to 

 demonstrate a partial fixation of complement by using more than 

 several units of the amboceptor, and when several units are em- 

 ployed the test suffers in delicacy. The second effect is still more 

 disturbing than the first. It depends upon partial dissociation of 

 the complement from its combination with the antigen and anti- 

 body compound. A quantity of syphilis antibody just sufficient 

 to fix 0.1 c.c. of the complement against two units of the ambo- 

 ceptor is no longer efficacious to hold back the complement from 

 partial liberation against the influence brought on by more than 

 four units of the amboceptor. The fixation of the complement by 

 two and three units of syphilis antibody respectively is also quite 

 ineffective to prevent hemolysis when ten and twenty units of the 

 amboceptor are added. Under these conditions the test fails to 

 indicate the presence of any syphilis antibody although it is really 

 present. When eight units of syphilis antibody are employed the 

 fixation of complement becomes so firm that twenty units of the 

 amboceptor can no longer bring about its liberation. 



