TITRATION OF COMPLEMENT 



On the basis of the two titrations outlined above, it is estimated 

 that at least 0.04 c.cm. complement is necessary to activate o.ooi c.cm. of 

 hemolysin. If less complement is used with the same amount of hemolysin, 

 hemolysis does not occur or else it is incomplete. If the quantity of hemol- 

 ysin is increased for instance threefold, then it will be found that 0.02 c.cm. 

 of complement suffices to produce hemolysis. Vice versa with an excess of 

 complement the hemolysin titer of o.ooi c.cm. may be reduced. How- 

 ever, there are narrow limits to this mutual compensatory action. 



Cytotoxins, Cytolysins. 



The hemolysin bodies are characteristic and important members of a 

 general class of substances known as cytotoxins, especially investigated by 

 Metchnikoff and his co-workers. 



Just as the immunization with erythrocytes led to the production of 

 lytic amboceptors which in connection with complement destroyed and 

 dissolved their antigens, so in a similar manner, various substances more or 

 less specific for their antigens have been produced through immunization 

 with leucocytes "Leucocidin," with nerve tissue, "neurotoxin," with 

 spermatozoa, "spermatoxin," and kidney tissue, "nephro toxin." The 

 proof of their action, particularly of neuro-, nephro-, and hepatotoxin is 

 not simple. As all these cytotoxic sera have at the same time a hemolytic 

 action, it is not easy to decide to what extent the changes in the organs 

 observed after the injection of the cytotoxic substances are dependent upon 

 the action of hemolysins. It must further be taken into consideration that 

 none of these sera are absolutely specific for the organ in question. This is 

 not surprising, inasmuch as there are widespread common group charac- 

 teristics (common receptors) among the different organs serving as antigens, 

 and only very few groups of a specific nature. The hopes which, at the 

 beginning, were placed upon the study of cytotoxins particularly with the 

 expectation that they would tend to become diagnostic and therapeutic 

 methods for the treatment of malignant tumors, have as yet been unreal- 

 ized. The entire field of cytotoxins urgently requires further investigation. 



