ANAPHYLAXIS 265 



the injection into an animal of a foreign protein — vegetable, 

 animal or bacteri£tl, simple or complex — followed by a 

 second injection after a proper length of time leads to a 

 series of symptoms indicating poisoning, which may be so 

 severe as to cause the death of the animal. Richet's term 

 "anaphylaxis" has been applied to the condition of the 

 animal following the first injection and indicates that it is 

 in a condition of supersensitiveness for the protein in ques- 

 tion. The animal is said to be "sensitized" for that protein. 

 The sensitization is specific since an animal injected with white 

 of chicken's egg' reacts to a second injection of chicken's 

 egg only and not pigeon's egg or blood serum or any 

 other protein. The specific poisonous substance causing the 

 symptoms has been called " anaphylotoxin" though what it 

 is, is still a matter of investigation. It is evident that some 

 sort of an antibody results from the first protein injected 

 and that it is specific for its own antigen. 



A period of ten days is usually the minimum time that 

 must elapse between the first and second injections in guinea- 

 pigs in order that a reaction may result, though a large pri- 

 mary dose requires much longer. If the second injection is 

 made within less time no effect -follows, and after three or 

 more injections at intervals of about one week the animal 

 fails to react at all, it has become "immune" to the protein. 

 ]?urthermore, after an animal has been sensitized by one 

 injection and has reacted to a second, then, if it does not 

 die from the reaction, it fails to react to subsequent injec- 

 tions. In this latter case it is said to be "antianaphylactic." 



It must be remembered that proteins do not normally get 

 into the circulation except by way of the alimentary tract. 

 Here all proteins that are absorbed are first broken down 

 to their constituent amino-acids, absorbed as such and these 

 are built up into the proteins characteristic of the animal's 

 blood. Hence when protein as such gets into the blood it is 

 a foreign substance to be disposed of. The blood contains 

 proteolytic enzymes for certain proteins normally. It is also 

 true that the body cells possess the property of digesting 

 the proteins of the blood and building them up again into 

 those which are characteristic of the cell. Hence it appears 



