176 



THE PRINCIPLES OF IMMUNOLOGY 



mentary activity in a dose of 0.3 c.c., then o.i c.c. is used in the test. The fully 

 controlled test would then be set up as follows : 



Reading from above downward, the second tube shows 0.25 c.c. typhoid 

 emulsion diluted 2 to 5, thus corresponding in bulk of original emulsion, to the 

 bulk of coli emulsion in 0.5 c.c. of a 1-5 dilution. It is necessary to use the 

 smaller bulk of coli emulsion in order to prevent anti-complementary activity. 

 Both quantities of typhoid emulsion are sufficient to fix the complement, whereas 

 the coli emulsion (tube 3) does not. The next three tubes which are controls show 

 that neither typhoid emulsion, coli emulsion nor anti-typhoid immune serum 

 have any anti-complementary activity. The last two tubes show that the com- 

 plement is in sufficient concentration to operate and that the sensitized erythro- 

 cytes will not of themselves hemolyze under the conditions of the experiment. 

 If the results prove to be confusing it is necessary to make additional controls 

 to determine if any of the reagents is hemolytic. This contingency is extremely 

 rare if proper care is given in their preparation. The test in this form shows 

 that the reaction is specific. 



Inhibition Zones. The phenomenon of complement fixation ex- 

 hibits certain of the characters noted in regard to other immune reac- 

 tions, not only in the titration of the reacting bodies but also in the 

 formation of the so-called inhibition zones and in the group reaction. 

 These latter features are best illustrated with the fixation of comple- 

 ment by immune sera prepared from the use of dissolved protein. 

 Gengou, a year after the publication of Bordet and Gengou, showed 

 that the inoculation into an animal of dissolved proteins, such as egg- 

 white, could lead to the formation of bodies which participate in com- 

 plement fixation with the specific antigen. This was confirmed by 

 Moreschi and later by Neisser and Sachs. The latter authors applied 

 the reaction to the forensic determination of protein. Gengou was of 

 the opinion that the immunization of animals with dissolved protein 

 led to the formation not only of precipitins but also of complement-fixing 

 bodies. The relation between these two immune substances will be 

 discussed after presenting data concerning inhibition zones and group 

 reaction. An experiment from the work of Neisser and Sachs serves 

 to illustrate the fact that immune serum may be used in the reaction 

 in such strong concentration as to inhibit fixation of the complement. 

 For this purpose they arranged two series of tubes. In series A they 

 placed decreasing amounts of the specific immune serum, a constant 

 quantity of 0.2 c.c. of 1-2000 solution of the antigenic human serum 

 and o.i c.c. fresh guinea-pig complement. In series B the same con- 

 stituents were placed with the exception of the immune serum which 

 was replaced in each tube by 0.2 c.c. salt solution. These mixtures 

 were incubated at 37 C. and then sensitized red blood-corpuscles were 



