COMPLEMENT-FIXATION TEST 253 



by using blood of an hcmwlogous ("same kind") animal. 

 Hence Ehrlich suggested the use of apes for preparing bac- 

 tericidal sera for human beings. (4) The bacteria may be 

 localized in tissues (lymph glands), within cavities (cranial, 

 peritoneal), in hollow organs (alimentary tract), etc., so that 

 it is not possible to get at them with sufficient serum to 

 destroy all. This difficulty is obviated by injecting directly 

 into the spinal canal when Flexner's antimeningococcus 

 serum is used. (5) Even if the bacteria are dissolved it does 

 not necessarily follow that their endotoxins are destroyed. 

 These may be merely liberated and add to the danger of the 

 patient, though this does not appear to be a valid objec- 

 tion. (6) Complement which is present in such a large excess 

 of amboceptor may just as well unite with amboceptor 

 which is not united to the bacteria to be destroyed as with 

 that which is, and hence be actually prevented from dissolv- 

 ing the bacteria. Therefore it is difficult to standardize the 

 serum to get a proper amount of amboceptor for the com- 

 plement present. 



COMPLEMENT-FIXATION TEST. 



Although little practical use has been made of bactericidal 

 sera, the discovery of receptors of this class and the peculiar 

 relations between the antigen, amboceptor and complement 

 have resulted in developing one of the most delicate and 

 accurate methods for the diagnosis of disease and for the 

 recognition of small amounts of specific protein that is in use 

 today. 



This method is usually spoken of as the "complement-fixa- 

 tion" or the "complement-deviation test" ("Wassermann 

 test" in syphilis) and is applicable in a great variety of mi- 

 crobial diseases, but it is of practical importance in those 

 diseases only where other methods are uncertain — syphilis 

 in man, concealed glanders in horses, contagious abortion 

 in cattle, etc. 



The principle is the same in all cases. The method 

 depends, as indicated above, on the ability of complement 

 to combine with at least two amboceptor-antigen systems, 



