310 



COLLECTED STUDIES IN IMMUNITY. 

 TABLE XI. 



Now if the cobra venom sensitized the blood-cells for the lecithin, 

 less lecithin would be required for solution the more cobra venom 

 were added. As a matter of fact the reverse is the case. When we 

 used a large excess of poison, five times as much lecithin was re- 

 quired for complete solution as when smaller doses were used. This 

 is readily explained by assuming that a large excess of amboceptor 

 causes a deflection of the lecithin, a phenomenon which we have 

 already met with in the endocomplements. 



The phenomena observed by us also serve to explain most easily 

 the inhibiting action exerted by certain sera. As is well known, 

 lecithin is able to combine with albuminous bodies, sugars, etc. If 

 this union is so firm that it is not disrupted by the affinity of the 

 cobra amboceptor, it will be impossible for the lecithin to come into 

 action. This is the case, for example, with ox serum, which when 

 fresh does not exert a trace of activation on goat blood, and yet 

 the ox serum contains sufficient lecithin, as we know by examining 

 its alcoholic extract. 



Ox serum is even able to prevent haemolysis on the addition of 

 free lecithin, the reason being evidently because it contains an excess 

 of inhibiting substances. On heating the serum these substances 

 lose their action to a greater or less extent, so that the serum is able 

 when mixed with cobra venom to effect haemolysis. As already 

 mentioned, however, the haBmolytic action is usually considerably 

 stronger when the sera are heated to 100 C. instead of only to 65 C. 

 Perhaps this is due to substances possessing different degrees of 

 thermolability. 



In other cases only a very slight difference is to be observed 



