654 COLLECTED STUDIES IN IMMUNITY. 



In order to analyze the result of this experiment, it will be 

 advisable to first have a clear idea as to the constitution of the 

 sediments in the two series previous to the addition of the comple- 

 ment. In series A the sediment consists of: 



1. The blood-cells laden with amboceptor. 



2. The antiamboceptor (if such is present in the antiserum) 

 bound to the complementophile group of the amboceptor. 



3. It may contain the precipitate formed by the combination of 

 albuminous constituents of the rabbit serum with the antiserum. 



In series B the sediment also contains blood-cells laden with 

 amboceptor, but there is, of course, no antiamboceptor. The con- 

 ditions for the formation of the precipitate, however, are exactly 

 the same as in series A, for in both series the same quantity of normal 

 albuminous constitutents of rabbit serum are present. 



In series B, if we disregard the slight inhibition with large doses 

 of antiserum, we find that the blood cells in all the tubes have been 

 completely dissolved. This can only mean that either the sediments 

 contained no precipitate, or that the precipitate present was unable 

 to exert its deflecting power on complement. It follows that ike 

 marked inhibition of haemolysis observed in series A must be ascribed 

 to the action of antiamboceptor s. 



Against this interpretation it might be objected that perhaps 

 the sediments of series A also lack an antiamboceptor, and that the 

 inhibition of haemolysis is due to the deflection of complement by 

 the precipitate. It would then be necessary to assume that the 

 goat amboceptor possessed a stronger affinity for the complement 

 than did the rabbit amboceptor, in consequence of which no deflection 

 of complement was produced by the precipitates in series B. In 

 order to meet this objection we have devised another experiment, 

 making use of the rabbit amboceptor as before, and excluding the 

 antiamboceptor while still maintaining the same favorable con- 

 ditions for the formation of a precipitate. The experiment is 

 made as follows: 



Decreasing amounts of antiserum are mixed with 0.0015 cc. inactivated 

 normal rabbit serum, and the mixtures kept at room temperature for forty-five 

 minutes. To each tube is then added 1 cc. 5% ox blood, the mixtures kept 

 at 37 for one hour, and then centrifuged. The sediments are mixed with 

 0.0015 cc. rabbit amboceptor plus 0.075 cc. guinea-pig serum. It will be seen 

 that the experiment corresponds to that described in Table I, A, except that 

 in place of the specific amboceptor, an equal volume of normal serum is mixed 



