574 IMMUNITY 



delicacy of the reaction and the ease with which it can be 

 observed, have been the means of throwing much light on the 

 process of lysogenesis, and thus on one part of the subject of 

 immunity. A short account of their properties may now 

 be given. 



Hcemolytic and other Sera. — It has long been known that 

 in sbme instances the blood serum of one animal has, in 

 a certain degree, the power of dissolving the red corpuscles of 

 another animal of different species ; in other instances, however, 

 this property cannot be detected. Bordet showed that if one 

 animal were treated with repeated injections of the corpuscles 

 of another of different species, the serum of the former acquired 

 a marked hsemolytic property towards the corpuscles of the 

 latter, the property being demonstrated when the serum is added 

 to the corpuscles. He also found that the hsemolytic property 

 disappeared when the hsemolytic serum was heated at 55° C, 

 but, as in the case of a bacteriolytic serum, was regained on the 

 subsequent addition of some serum from a fresh {i.e., non-treated) 

 animal. These observations have been fully confirmed and 

 greatly extended. Ehrlich and Morgenroth analysed the 

 phenomena in question, and showed that the specially developed 

 and heat-resisting substance, "immune-body," entered into com- 

 bination with the red corpuscles at a comparatively low tempera- 

 ture, namely, at 0° C. ; whereas complement does not combine 

 at this temperature. In this way a method is supplied by 

 which the immune-body can be removed from a hsemolytic 

 serum while the complement is left. They came to the conclu- 

 sion that immune-body combined with the complement, though 

 the combination was less firm and only occurred at a higher 

 temperature — best about 37° C. They therefore consider that 

 the immune-body acts as a sort of connecting-link between the 

 red corpuscle and the complement, hence the term " amboceptor " 

 which Ehrlich afterwards applied. It may be stated, however, 

 that the direct union of complement and immune-body has not 

 been conclusively demonstrated. Muir and Browning, for 

 example, found that when a fresh serum is passed through a 

 Berkefeld filter, complement is largely retained in the pores 

 of the filter, whereas immune-body passes through practically 

 unchanged ; and that if a mixture of complement and immune- 

 body be made and filtered at a temperature of 37° C, the 

 amount of immune-body which passes through is not diminished, 

 whereas it would be if it had united with the retained comple- 

 ment. Accordingly by this method there was obtained no 

 evidence of the direct union of immune-body and complement. 



