TECHNIQUE OF BACTERICIDAL TEST-TUBE EXPERIMENTS. 353 



employed without causing bactericidal action by the normal serum 

 itself. 



The dose of complement should be such that the plate containing 

 only complement and the culture differs very little from the control 

 of the culture sowing alone. Too large a quantity of complement 

 should be avoided; certain!)' in no case should more than about 0.5 cc. 

 complementing serum be used. The technique then is as follows: 

 1.0, 0.3, 0.1, 0.03, 0.01 cc. of inactive immune serum are placed into 

 a series of test-tubes ; to each of these is then added the same amount 

 of the complementing active normal serum (e.g. 0.3 cc.) and the 

 bacterial culture. All of the tubes are then made up to the same 

 amount (2 to 3 cc.) with physiological salt solution, and finally each 

 tube receives three drops of bouillon. The controls in this case 

 must be still more numerous. The sterility of each serum must be 

 demonstrated, as well as the fact that the inactive immune serum by 

 itself and the active normal serum by itself are inert. 



The result of such an experiment is usually startling at first sight 

 because the plates which had the largest amounts of immune serum 

 show the largest number of colonies. One must therefore always 

 bear in mind the deflection of complements in consequence of an 

 excess of immune body. The paradoxical results caused by this 

 deflection of complement is seen not only in the plates but also in 

 the test-tube experiment. The various ways in which the comple- 

 ment is deflected from its destination have already been discussed 

 in a previous chapter. In bactericidal experiments the deflection 

 caused by an excess of the amboceptors produced by immunization 

 is especially important. In a mixture of bacteria, complements, and 

 large amounts of amboceptor, the complement is bound not only by 

 the amboceptors anchored to the bacteria but also in large measure 

 by " free '' amboceptors which are not anchored to bacteria. A 

 portion of the anchored amboceptor therefore finds no complement 

 at its disposal and is, therefore, unable to exert any bactericidal 

 action. In this way there arises a relative lack of complement. 

 This can occur especially if part of the amboceptors has become 

 changed into an amboceptoid with increased affinity (Wechsberg, 1 

 E. Neisser and Friedemann 2 ) . In bactericidal experiments, how- 

 ever, the cooperation of the amboceptoids has not yet been proved. 



The completion of amboceptors can be disturbed in another way. 



1 Wiener klin. Wochensch. 1902. 2 Berl. klin. Wochensch. 1902. 



