286 COMPLEMENT AND OPSONIN 



whole of the staphylococcic opsonin may be removed by the 

 addition of sufficient amounts of tubercle bacilli. 1 



A second fact, closely allied and perhaps in reality identical 

 with the foregoing, is the rise in a particular opsonin after an 

 injection of a suitable vaccine, the others remaining constant. 

 This rise cannot be accounted for (in my opinion, at least) by 

 the appearance of small quantities of thermostable opsonin, 

 since it may occur when this substance cannot be found in the 

 serum. 



On the other hand, there are very remarkable analogies between 

 the two substances. In each there is the same difference of 

 opinion as to whether it occurs in normal plasma, or is only 

 developed when clotting and destruction of leucocytes occur. 

 Wright and Douglas found the amount of opsonin present in 

 serum and in citrated plasma exactly the same, whereas Briscoe 

 found that very little phagocytosis took place when staphylococci 

 were injected into a surviving heart in which no clotting took 

 place. These divergencies are quite similar to those found by 

 different investigators in the case of complement. 



Again, it has been already shown that when a blood-clot 

 contracts, the first serum which can be collected is poor in com- 

 plement compared with that which follows, and that after a time 

 the amount again diminishes. An exactly similar phenomenon 

 may sometimes, though apparently not always, be demonstrated 

 with opsonin (Henderson Smith). Hence an important practical 

 point : the patient's blood should always be collected at the same 

 time as the control in determinations of the opsonic index. 



Thirdly, it has been shown by Levaditi that the aqueous 

 humour of the rabbit contains no complement and but a trace of 

 opsonin. But when the fluid which recollects after puncture was 

 examined, it was found to be rich in both substances. He found 

 a similar relation between the two substances in oedema fluid. 

 As against these results we have to put the researches of Leding- 



1 Since the above was written Muir and Browning have adduced very definite 

 evidence of a partial specificity in the case of the complements. They find 

 that the bactericidal action of normal serum may be due to the direct action 

 of complements, and that, on weakening normal serum by successive additions 

 of dead bacteria, the first effect is a falling off in the bactericidal action as 

 tested on that bacterium. Then the bactericidal action on the other bacteria is 

 diminished, and with a larger addition the haemolytic complement is absorbed. 

 This indicates features exactly like the partial specificity seen in opsonins, 

 and a similar absorption without the intervention of an immune body. 



