CHAPTER VII. 

 ANAPHYLAXIS, ALLERGY OR HYPERSENSITIVENESS. 1 



PROTEIN fed to man or animals is reduced to simple compounds, 

 chiefly amino-acids, by the action of gastro-intestinal enzymes before 

 it is absorbed from the alimentary canal. These gastro-intestinal 

 enzymes act rapidly under normal conditions, and without an appre- 

 ciable latent period. One noteworthy result of digestion is a complete 

 denaturization of all ingested protein before it enters the tissues of 

 the host; absorption of unaltered or partially-digested protein is 

 prevented or reduced to a minimum. 



The importance of a denaturization of protein before it enters the 

 tissues becomes apparent when a comparison is made between the 

 effects of parenteral injections of the end-products of protein digestion 

 on the one hand, and of the unaltered protein itself on the other hand. 

 Repeated parenteral injections of amino-acids in moderate amounts 

 appear to be without serious or noteworthy effects upon experimental 

 animals. A single parenteral injection of an unaltered protein is also 

 without visible effect, as a rule. A second parenteral injection of the 

 same protein, after an interval of ten to fourteen days, frequently is 

 followed by a rather definite train of symptoms, severe in character 

 and wholly unlike the negative response to a corresponding treatment 

 with amino-acids or normal end-products of gastro-intestinal digestion. 



Sensitization. The first parenteral injection of a protein 2 which 

 is foreign to the body, or in some instances, natural for the body but 

 alien for the blood, is without visible effect upon the animal, but leads 

 to its sensitization to the specific protein. The sensitizing agent is 

 variously referred to as a sensitizer, sensibilisinogen, or anaphylac- 

 togen, and may be effective in very small doses. Rosenau and Ander- 

 son 3 were able to sensitize guinea-pigs with one-millionth of a cubic 

 centimeter of horse serum; Wells 4 has sensitized the same animal 



1 For an excellent resume of the literature of anaphylaxis complete to 1912, see 

 Hektoen, Jour. Am. Med. Assn., 1912, Iviii, 1081. 



2 Proteins deficient in tryptophane or tyrosin are said not to sensitize. 



3 Bull. 29 and 36, Hygienic Laboratory, Washington, D. C., 1906, 1907. 

 Wells' Clinical Pathology, 1914, 2d ed., 180. 



