636 COLLECTED STUDIES IN IMMUNITY. 



The table shows the same condition which we have already noted 

 in the hsemolysis of guinea-pig blood. The haemolysis of the prepared 

 ox blood too, proceeds more rapidly if the horse serum and inactive 

 ox serum are mixed some time before the addition of the blood-cells. 

 From this it follows that some sort of a reaction takes place between 

 constituents of the horse serum and of the ox serum. A really 

 active complex as in the haemolysis of guinea-pig blood cannot thus 

 be formed, for, as we have repeatedly pointed out, the ox serum 

 cannot functionate as an amboceptor. We shall probably not err 

 if we assume that the inactive ox serum participates in the hsemolysis 

 of the prepared ox blood by anchoring a constituent of horse serum 

 which inhibits the action of the horse complement responsible for 

 hsemolysis. An autoanticomplemeiit of horse serum is out of the 

 question, if only for the reason that the horse complement is bound 

 by the prepared ox blood-cells. On the other hand it seemed very 

 possible that the horse serum constituent in question which inhibits 

 haemolysis and which is bound by ox serum, possessed the character 

 of a complement or a complementoid. The action of this second 

 complement of horse serum would be this, that it does not dissolve 

 prepared ox blood, but possesses a higher affinity than the effective 

 complement. The anchoring of this constituent would cause the 

 effective complement to be bound at an unsuitable situation where 

 it is not dominant. In order to prove the correctness of this view 

 it is necessary to show that the binding of the effective horse com- 

 plement to the prepared ox blood, and the hsemolysis of prepared ox 

 blood by the joint action of active horse serum and inactive ox 

 serum, are two independent reactions. In other words we must 

 effect a binding of the active principle of horse serum and yet have 

 no hsemolysis when under exactly the same conditions inactive ox 

 serum is also present. This we have succeeded in doing. It is 

 very easy to fulfil the .conditions just mentioned, by digesting the 

 ox blood with a smaller quantity of amboceptor. We proceeded as 

 follows: 



Two series of tubes are prepared, each tube containing 1 cc. 5% ox blood 

 and decreasing amounts of amboceptor (inactivated serum of a rabbit immunized 

 against ox blood). After remaining at 37 for one hour, the mixtures were 

 centrifuged. The sediments were then treated as follows: 



Series A. Digested with a mixture of 0.2 cc. horse serum plus 0.1 cc. inactive 

 ox serum. 



Series B. Digested with 0.2 cc. horse serum ' for one hour at 37, centrifuged,. 

 and the sediments thus obtained mixed each with 0.1 cc. inactive ox serum. 



