H^EMOLYTIC AND OTHER SERA 573 



becomes diminished and may be practically annulled. This 

 result, which is generally known as the " Neisser-Wechsberg 

 phenomenon," has been the subject of much controversy, and 

 cannot yet be said to be satisfactorily explained. It would 

 accordingly be out of place to discuss here the different views 

 with regard to it. (Regarding some theoretical considerations 

 as to the therapeutic applications of antibacterial sera, vide 

 p. 571.) 



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 haemolytic 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, 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 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 tempera- 

 ture, 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 haemolytic 

 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 



