BACTERIA, AMBOCEPTOR, AND COMPLEMENT 71 



with the bacteria, whereas the amboceptor is readily anchored to the 

 organisms. This can be shown by treating serum with killed bac- 

 teria (of suitable kind) at a temperature of C., and subsequently 

 removing these by centrifugation. The absorption of the ambo- 

 ceptor is then shown by the fact that such serum is no longer capable 

 of causing the destruction of living organisms of the same order, 

 while the addition of such extracted but fresh serum to inactive 

 (heated), non-extracted serum will render this actively bactericidal. 

 The rationale of this will be readily understood by reference to 

 Fig. 1 and bearing in mind the relative thermostability of the ambo- 

 ceptor as compared with the complement. 



Mechanism of Interaction between Bacteria, Amboceptor, and Com- 

 plement. Much of our knowledge of the mechanism which is involved 

 in the interaction between bacteria, amboceptor, and complement 

 has been reached from a study of the closely corresponding glo- 

 bulicidal (hemolytic) properties which certain sera possess for red 



FIG. 1 



Bacterium Amboceptor Complement 



corpuscles of animals of alien species. Working with washed cor- 

 puscles, the compound character of the hemolysin, and the absorp- 

 tion of the amboceptor by the cells, can be very well demonstrated 

 as follows: Red corpuscles from an animal of a suitable species are 

 washed free from serum with saline (by centrifugation), and then 

 suspended for a couple of hours in an actively hemolytic serum, the 

 mixture being kept at a temperature of from to 3 C. They are 

 then thrown down again by means of the centrifuge, when the super- 

 natant fluid is tested at body temperature, on the one hand against 

 untreated washed corpuscles, and on the other against those used 

 in the extraction. In the latter case hemolysis will result because the 

 corpuscles have absorbed the hemolytic amboceptor and are now 

 subjected to the action of the complement, union with wl}ich evi- 

 dently does not occur at the low temperature at which the extrac- 

 tion was carried out. In the case of the untreated corpuscles no 

 hemolysis is observed, because the amboceptor has been previously 



