HISTORIC DEVELOPMENT OF IMMUNOLOGY 57 



laise and general urticaria occur. The urti- 

 caria usually does not appear until about the 

 third day. In an extremely small proportion 

 of cases (1 to 50,000, according to Park), the 

 anaphylactic symptoms are characterized by 

 labored respiration, cyanosis, collapse, uncon- 

 sciousness, and death. The entire picture is 

 an exact counterpart of the anaphylactic shock 

 so readily produced by a second injection of 

 horse serum into the guinea-pig. 



Mechanism This phenomenon was first de- 

 scribed by Auer and Lewis and is attributed by 

 these investigators to spasm of the smallest 

 bronchioles. This spasm virtually causes suf- 

 focation of the animal, inasmuch as air cannot 

 pass either in or out of the lungs. Thus, the 

 phenomenon is not due to any actual poisons 

 in the horse serum, but results entirely from a 

 hypersusceptibility of the individual whose 

 tissue-cells split up the foreign protein of the 

 serum into highly poisonous intermediary 

 products, to which the toxic symptoms are due. 



Schultz and Jordan have shown experiment- 

 ally that serum anaphylaxis is essentially a 

 matter of hypersensitization of smooth muscle 

 in general, and they suggest that the occasional 



