ACTION OF MICRO-ORGANISMS 



207 



used. The anaphylactic condition is due to the reaction of 

 all the cells of the body.f 



All the above serum reactions have certain features in 

 common. They all require the presence of two substances : 

 one to produce the action (complement) and the other to unite 

 the complement to the substance which is acted upon (alexin) . 

 The second substance is called the amboceptor. This is 

 like the chemistry of dyeing, in which one molecular group 

 confers the colouring property and another group the power of 

 uniting with the fabric. Sometimes a mordant is required 

 before the dye will unite with the fabric. 



The complement is not specific, but it is rapidly destroyed 

 by heating the serum to 55 C. ; that is, it is thermolabile. 

 Such inactivated serum is used in studying the phenomena of 

 immunity as the amboceptor remains undamaged. 



The amboceptor is specific and is thermostable ; as stated 

 above an activated serum is used to study the amboceptor. 

 By adding fresh complement (in non-immune serum) to 

 inactivated immune serum the activity is restored. By 

 varying the proportions of fresh serum and inactivated immune 

 serum the dosage of amboceptor and complement may be 

 determined. 



The following experiment illustrates these points : 



TABLE XXXVII 



We must here refer to zymoids (p. 73) which we saw were 

 substances derived from enzymes that cannot digest their 

 proper substrate but prevent the action of other enzymes. 

 This behaviour is explained by assuming that enzymes are 

 composed of amboceptor and complement. If the comple- 



* H. H. Dale, /. Pharm. and exper. They., 1912, vol. 4, p. 167. 



