158 IMMUNE SERA 



which is specific, but only the mode of its produc- 

 tion. The production of anaphylatoxin requires the 

 action of antibodies; the mere solution or disinte- 

 gration of bacteria by other means does not suffice. 

 In other words, a definite cleavage of the proteid 

 molecule is necessary. The anaphylatoxin, there- 

 fore, is not identical with Pfeiffer's "endotoxins," 

 though perhaps the latter may be the mother sub- 

 stance from which the anaphylatoxin is derived. 



Another important factor in pathogenesis, accord- 

 ing to Bail, is the ability of many bacteria to pro- 

 duce certain neutralizing substances, not directly 

 injurious, but able to inhibit or neutralize the anti- 

 bacterial activities of the body. These substances 

 Bail calls aggressins. There is still some doubt 

 whether they are a distinct class of bacterial 

 products. Wassermann and Citron, Doerr, and 

 others regard them as consisting of dissolved 

 bacterial substances, extracted endotoxins and 

 toxins. 



Resistance Against Infection. The ability of 

 an animal to resist the effects of a pathogenic 

 organism is spoken of as immunity, and may be 

 either natural or acquired. For example, it is well 

 known that the lower animals are immune against 

 syphilis and gonorrhoea, that dogs and goats are 

 rarely affected with tuberculosis, and that man is 

 naturally immune against chicken cholera and 

 rinderpest. These are instances of natural im- 



