536 IMMUNITY 



with regard to it. (Regarding some theoretical considerations 

 as to the therapeutic applications of antibacterial sera, vide 

 p. 534.) 



The laws of lysogenesis are, however, not peculiar to the 

 case of solution of bacteria by the fluids of the body, but, as has 

 been shown within the last few years, hold also in the case of 

 other organised substances, red corpuscles, leucocytes, etc., when 

 these are introduced into the tissues of an animal as in a process 

 of immunisation. Of such sera the hsemolytic have been most 

 fully studied, and, owing to the 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 been known for some time 

 that in some 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, how- 

 ever, 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 haemolytic 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 

 temperature, namely, at 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 hamiolytic 

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

 clusion 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 " ambo- 

 ceptor " 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, 



