22 PROPERTIES OF ILEMOLYTIC SERA 



exclude one another in haemolytic combinations, and have 

 thus apparently a similar haptophore group ; in fact, as 

 we have elsewhere stated, there is a certain community or 

 general character in the combining relationship of different 

 complements. We may further point out that some of the 

 differences observed in complements are of quantitative 

 rather than of qualitative nature. For example, various 

 bacteria absorb bactericidal complement as tested on a 

 particular organism before they take up haemolytic com- 

 plement, but if a sufficient amount of bacterial emulsion 

 be used the haemolytic complement will also be absorbed. 

 This matter of the degree in the combining affinities has 

 been to a large extent overlooked by workers on the subject. 

 The sensitizing of a molecule, therefore, does not imply the 

 creation of a new combining group corresponding to the 

 supposed special characters of the haptophore group of com- 

 plement, but merely the production of some change in a 

 molecule which allows a substance (complement) with very 

 general combining affinities to enter. It is also shown 

 below that the nature of the receptor is an important factor 

 in determining whether or not complement will be taken 

 up after the union of immune-body. In the case of sensitized 

 ox's corpuscles, the maximum absorption of ox's comple- 

 ment is almost reached with one dose of immune-body ; 

 subsequent addition of similar molecules of immune-body, 

 though these enter into combination with the receptors, 

 does not lead to increased absorption of complement. 

 This result must depend upon the receptors. Although the 

 question as to the constitution and mode of action of im- 

 mune-body cannot be considered to be completely settled, we 

 believe, in view of all the facts that complement is brought 

 into union with the cell receptors as a result of the action 

 of immune-body. The existence of a special comple- 

 mentophile group in the latter is not proved, and the use of 

 the term * amboceptor ' does not appear to be justified. 



