l6 QUATERCENTENARY STUDIES IN PATHOLOGY 



presence of a large amount of amboceptor. On the other hand, in 

 highly immune sera, the opsonic property of the serum, after heating, 

 may still be present to a marked extent, and in general, as is shown later 

 on, the more highly immune a serum is the less is the difference in opsonic 

 effect between the heated and unheated sera. Again, from the dilution 

 experiments recorded above, it is evident that, after the serum has been 

 diluted to such a degree that the complement is no longer present in an 

 amount sufficient to cause haemolysis, yet the serum in the unheated 

 state exercises a greater opsonic effect than in the heated condition in 

 corresponding dilutions. 



Even if it be admitted that Dean's suggestion is feasible, yet to 

 explain the action one would have to suppose that the amboceptor 

 possesses two groups, one of which is a complementophilic, the other a 

 special function group. Thus, though the action of the complement 

 were suppressed, such an immune substance, in virtue of the action of 

 its special function group, might still be capable of inducing 

 phagocytosis. Even admitting this, the fact would still remain that the 

 substance is a new one, and not of the exact nature of any immune 

 substance previously described, and to such a substance the term opsonin 

 might reasonably be applied. 



There are two further points to which reference may be made. The 

 first is the difficult question of the leucocytic origin of the complement. 

 Time has not permitted of experiments on this problem, but one 

 observation may be referred to. If one perform phagocytic tests in the 

 usual way, with an unheated haemolytic scrum, whether normal or 

 immune, human leucocytes, and the red blood corpuscles of an ox, 

 guinea-pig, etc., blood shadows appear in the leucocytes. This 

 phenomenon appears almost instantaneously at 37° C. In the case of 

 unheated guinea-pigs' serum and rabbits' corpuscles, it was found that, 

 after three minutes at 37° C, blood shadows appeared in the leucocytes. 

 On the other hand, using an immune heated haemolytic serum after one 

 hour at 37° C, the red corpuscles in the leucocytes were apparently still 

 unchanged. No haemolysis had taken place. But if, as Metchnikoff 

 and his followers have stated, the phagocytes contain the cytases or 

 alexines, then one should have expected haemolysis to take place inside 

 the leucocytes. The above observations, however, tend to show that 

 such is not the case. 



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