204 A MANUAL OF BACTERIOLOGY 



the reaction occurs. As regards the quantities of reacting 

 substances, for a given amount of antigen there is a 

 definite range within which complement and anti-body 

 give rise to anaphylatoxin, but outside which, i.e. if 

 either be in excess or deficient, the toxin does not appear. 

 If the time be insufficient, the mixture is non-toxic ; if 

 the time be extended beyond certain limits, the mixture 

 is also non-toxic, because protein-cleavage proceeds so 

 far that the toxic substances are split up into simpler 

 non -toxic bodies. The lower the temperature, the slower 

 the formation of anaphylatoxin ; the optimum tempera- 

 ture is 37 C. This theory not only accounts for the 

 production of anaphylaxis, it also explains why anaphy- 

 laxis does not occur after repeated injections of antigen 

 (e.g. antitoxic serum) at shorter intervals than twelve to 

 fourteen days. In the latter case, anti-body is present in 

 so large amount that antigen is subjected at once to such 

 a degree of cleavage that the toxic stage is rapidly passed 

 and the non-toxic stage reached, and thus there is never 

 sufficient toxin present to cause symptoms. 



Others would base the reaction in anaphylaxis and other 

 forms of sensitisation upon a sudden dislocation of the 

 condition of static equilibrium of the colloids of the 

 blood. 1 



Anaphylaxis is of considerable importance in serum 

 treatment, e.g. where a patient has had a previous course 

 of serum treatment and has again to be treated with 

 serum. If this be the case, anaphylaxis may be pre- 

 vented by several procedures. If 5-10 c.c. of antigen 

 (i.e. the serum) be given per rectum, this having been 

 weU washed out, the individual is rendered refractory 

 in from ten to twelve hours, and subcutaneous or intra- 

 venous injections of serum may then be given with 



1 Widal, Abrami and Brissand. See Med. Sc., Abst. and Reviews, Vol II. , 

 1920, p. 369. 



