TWENTY-FIVE YEARS OF BACTERIOLOGY 133 



consists of a chemical or physico-chemical union between 

 the original antigen and the manufactured antibody, tak- 

 ing place in the body or in a test tube, through which the 

 primarily poisonous antigen is rendered innocuous. In 

 other words, the immune antigen-antibody complex is a 

 harmless compound. 



In a similar manner the sensitizing antigen and induced 

 antibody unite in anaphylaxis, but the product of the union 

 is essentially different from the one just considered, in 

 that it is highly injurious, and the effect of the antigen- 

 antibody complex is not to protect, but to poison the ani- 

 mal. The basic distinction between the immune and the 

 anaphylactic condition, as described, is further enforced 

 when we recall that the original toxic protein used to 

 immunize is detoxicated in the course of the immune re- 

 action and the original non-toxic protein used to sensitize 

 is endowed with the property of intense toxicity in course 

 of the latter reaction. 



As in the instance of the immune state, a still undecided 

 controversy is going on as to whether the hypersensitive 

 condition depends upon humoral or upon cellular factors. 

 There is no doubt that the anaphylactic antibody exists 

 free in the blood, and hence that a normal animal can be 

 rendered passively sensitive by the infusion of blood de- 

 rived from a sensitized animal. It is equally true that 

 the anaphylactic response is in part a cellular one, as in 

 the instance mentioned of the bronchial musculature stim- 

 ulated to contraction. By appropriate experiments it can 

 be shown that organs containing smooth muscle taken 

 from sensitive animals, exhibit the equivalent of the 

 anaphylactic reaction even outside the living body ; and 

 also that coincidentally with the appearance of the 

 "shock" of the reaction in the guinea pig, the blood be- 

 comes incoagulable. 



Hypersensitiveness may exist independently of pur- 

 posive artificial sensitization, and some of the most im- 

 portant examples of that condition have been observed 



