DEVIATION OF COMPLEMENT 157 



fixes complement. The fact that deviation may occur 

 where there is no precipitation would indicate that when 

 a serum is injected the all-important result is the develop- 

 ment of anti-substances, and these in combination with 

 certain substances in the serum have the property of fixing 

 complement. The combination of substance + anti-sub- 

 stance may be, and usually is, attended by precipitation. 

 Further, the results with regard to the relation of the 

 amount of complement fixed to the amount of precipitate, 

 suggest that the latter may vary in composition. An 

 analogy can be drawn between the anti-substances in 

 question and the haemolytic and bacteriolytic immune- 

 bodies. A striking difference, however, is presented by the 

 fact that increase in the amount of serum (receptors) beyond 

 a certain point leads to a diminution in the amount of 

 complement taken up a phenomenon which so far as we 

 know has not been observed in the case of other anti-sera. 

 The extraordinarily small amount of the homologous serum 

 which is sufficient to produce a recognizable deviation of 

 complement also appears unique in serum reactions. 



It has been recognized for a considerable time that when 

 the serum of an animal is injected into another animal of 

 different species, the serum of the latter acquires an ' anti- 

 complement ' property. It will be evident, however, from 

 what has been stated above, that when the anti-serum is 

 added to the serum, there are present the three essentials 

 for the deviation phenomenon, viz. (a) certain molecules 

 in the serum injected (homologues of receptors), (b) the 

 anti-substances to these molecules, and (c) complement. 

 Complement will thus be fixed and apparently neutralized. 

 Are there in addition true anti-complements, i. e. anti- 

 substances which unite directly with the haptophore group 

 of complement in the same way as anti-toxin unites with 

 toxin ? The possibility of this cannot be excluded, but 

 it is now clear that facts established with regard to anti- 



