PROPERTIES OF COMPLEMENTOIDS 67 



plement has a combining affinity. In the former case the 

 complement is converted into inactive complementoid ; 

 in the latter, if the substance with which it is combined 

 can be separated by centrifugalization, the complement 

 will be actually removed from the serum. In the former 

 case, if our theoretical considerations are correct; the serum 

 when used as a medium of suspension will interfere with 

 lysis ; in the latter this interfering action should be absent. 

 Acting on these ideas we have investigated how haemolysis 

 will progress in a serum from which the complement has 

 been removed. We can remove the complement from a 

 fresh serum by bringing it into contact with some cells or 

 bacteria treated with the corresponding immune-body 

 and then after time has been allowed for combination 

 remove the serum by centrifugalization. In this way a 

 serum practically free from complement as tested by hsemo- 

 lytic experiments is obtained. We have carried this out 

 by various methods, the most satisfactory of which is the 

 following. Washed corpuscles of the ox in 0-85 per cent, 

 salt solution are placed in a sterilizer overnight at 55 C., 

 they are then centrifugalized and the brownish fluid is 

 removed. The hsemolytic receptors of such heated cor- 

 puscles are, however, not destroyed ; they still have the 

 power of combining with immune-body and thereafter of 

 taking up complement. To a suspension of heated cor- 

 puscles a large amount of immune-body is added, and after 

 time is allowed for combination of the latter the corpuscles 

 are repeatedly washed in salt solution and centrifugalized ; 

 finally the fluid of the suspension is removed as completely 

 as possible, so as to avoid dilution of the serum. To the 

 corpuscles thus treated the fresh serum of the guinea-pig 

 is added and the mixture is thoroughly shaken up and placed 

 in the incubator at 37 C. for two hours ; the tubes are 

 then centrifugalized and the serum is pipetted off. If 

 sufficient amount of corpuscles and immune-body are used 



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