COMPLEMENT 161 



dilution, and hemolysis should be practically complete after twenty 

 to thirty minutes in a water-bath held at 37° C, although the 

 period of incubation is one hour. Rabbit complement and dog com- 

 plement are very unsatisfactory, since nonspecific fixation is quite 

 commonly encountered. 



Bond and Sherwood (1939) found that the hemolytic property of 

 snake serum is due to the action of a thermolabile complement and 

 a naturally occurring hemolysin. The complement in snake serum 

 possesses properties similar to guinea pig complement. The titer 

 is usually high; it is thermolabile and deteriorates on standing. 

 Furthermore it was bound by a specific bacterial antigen-antibody 

 complex and also by the syphilitic antigen-reagin complex respec- 

 tively. 



Specific Fixation of Complement. — In 1901 Bordet and Gengou 

 observed that sensitized bacterial cells adsorbed or bound comple- 

 ment and apparently proved that the complement that lysed sensi- 

 tized bacteria was identical with the complement that laked 

 sensitized red cells. This work, however, has not ended the con- 

 troversy over whether there is one complement or many comple- 

 ments, but it did give the scientific world the complement fixation 

 technique. The subject of multiplicity or singleness of complement 

 is discussed rather extensively by Zinsser, Enders and Fothergill 

 (1939). 



Specific Complement Fixation by Precipitates. — The follow- 

 ing year (1902) Cengou showed that precipitates formed in the 

 I)ro<'ipitin reaction would bind complement. Gengou explained this 

 as due to amboceptors or sensitizing antibodies present in the im- 

 nume serum along with precipitins. According to the unitarian 

 viewpoint supported by Zinsser and others, the sensitizer and 

 precipitin are identical, and while flocculation does not require 

 complement, the precipitate formed, which is composed of sensitizer 

 and antigen, is able to adsorb complement. Experimental support 

 for this has been offered by Gay (1905), Moreschi (1905), and 

 others. It was Gay who noted the relationship to the precipitin 

 reaction. 



Time of Occurrenck of Fixation. — Dean (1913) has shown 

 that the rate and character of precipitates formed influence the 

 fixation of complement. In his opinion the greatest fixation of 



