ANAPHYLAXIS AND HYPERSUSCEPTIBILITY 179 



experimental animal. Allergin may be demonstrated in the blood- 

 serum of such immunized animals. Immunity must, therefore, 

 be accounted for on a basis other than antianaphylaxis. It may 

 be that the cells no longer unite with the products of the action 

 of the allergin upon the antigen, or that another antibody has been 

 developed which inhibits the action of the allergin. The immune 

 animal is only relatively susceptible, and may be shown still to 

 be somewhat susceptible by appropriate experimentation. Ander- 

 son and Frost state " anaphylaxis is a step toward immunity, 

 which is conceived as an increased capacity for safely and rapidly 

 eliminating the specific antigen proteid." 



Relationship of Anaphylaxis to Certain Body Reactions. 

 The anaphylactic explanation of serum sickness in man has already 

 been discussed. Several cases are on record where injection of 

 diphtheria antitoxin has resulted in death within a few minutes. 

 Rosenau and Anderson have recorded cases in which the prophylac- 

 tic injection of antitoxic serum into normal individuals resulted in 

 explosive manifestations of anaphylaxis, such as a prickling sensa- 

 tion in chest and neck, labored breathing, paralysis, convulsions, 

 and death within five minutes after injection. It seems evident 

 that the individual was naturally hypersensitive. Fortunately, 

 such cases are extremely rare. The prophylactic and curative 

 value of diphtheria antitoxin far outweigh its dangers. 



Rosenau and Anderson have also recorded some evidence that 

 certain of the toxemias of pregnancy, particularly puerperal 

 eclampsia, are to be accounted for by a sensitization of the body 

 by the cells of the placenta. It was found that guinea-pigs might 

 be sensitized with the placenta of the same species by a single 

 injection, and a second injection later gave a typical anaphylactic 

 reaction. 



Bacterial Anaphylaxis. It has been shown by several inves- 

 tigators that proteins from bacteria may be used in sensitizing 

 animals against a second injection; in other words, they resemble 

 proteins from other sources in this respect. Extracts from Bacillus 

 coli, B. anthracis, B. tuberculosis, B. typhosus, and others have been 

 shown to sensitize. This fact has been deemed of considerable 

 practical importance in disease diagnosis. There is reason to 

 suppose that infection with certain bacteria will sensitize the body 



