240 MEDICAL BACTERIOLOGY 



1 . Syphilitic Antigen : 



Contains no amboceptor, if negative. 



2. Patient's Serum : c ..... \^^\ 



( Syphilitic amboceptor, if positive. 



.s/'VVN 



3. Complement (guinea-pigs): 



4. Amboceptor (immunized rabbits) : 



5. Red Blood Cells : 



There are here four known substances with which to determine the presence 

 or absence of a fifth, namely, syphilitic amboceptor = 



It is known that complement will join with amboceptor when that ambocep- 

 tor 's antigen is present; the complement is then fixed and can never join any 

 other amboceptor. Hence, if the serum of a syphilitic person is placed in a tube 

 with complement and syphilitic antigen and incubated for an hour the com- 

 plement is fixed. There is no free complement in the tube. 



U 



Incubated at 37C. for i hour. 

 Complement fixation. 



If the serum of a non-syphilitic person is placed in a tube with complement 

 and syphilitic antigen and incubated the complement is not fixed the comple- 

 ment remains free and unaltered. 



Incubated at 37C. for i hour. 



No Complement Fixation. 



As placed in the tubes the complement, human serum, syphilitic antigen 

 mixture is a clear, colorless fluid, almost like water in appearance. No change 

 in its appearance occurs when complement is fixed, therefore, it is necessary to 

 add something to these tubes that will indicate whether the complement re- 

 mained free or was fixed. For this purpose, after the complement, human 

 serum, syphilitic antigen mixture has been incubated for i hour, red blood cells 

 and the inactivated serum of a rabbit sensitized against such cells are added. 



