CHAPTER XVIII 



ANAPHYLAXIS AND HYPERSUSCEPTIBILITY 



THE body normally takes its food through the intestinal tract, 

 or by enteral introduction. Any foreign proteins introduced in 

 this manner are generally changed by digestion, so that they may 

 be used by the body-cells or assimilated. When introduced by 

 par enteral injection (outside the alimentary canal, as subcu- 

 taneously, intravenously, etc.) antibodies of different kinds are 

 produced. Thus far we have considered three antibodies which 

 antagonize bacteria or other antigens which are introduced, but 

 there exists still another type of body reaction, sensitization toward, 

 rather than immunization against, an antigen. This phenomenon 

 is exhibited only under certain conditions, and the body is then 

 said to show anaphylaxis or hyper sensitiveness to the antigen. 

 The significance can best be understood by a study of specific 

 examples. A number of these have been noted independently and 

 are deserving of mention. 



Phenomenon of Arthus. Arthus injected rabbits subcu- 

 taneously with horse serum at six-day intervals. The first three 

 injections were readily absorbed by the tissues, the fourth was 

 followed by some edema at the site of injection, and, after the 

 sixth or seventh injection, the skin at the site became gangrenous, 

 and a deep abscess scar was finally formed. If the sensitized 

 animal be injected intravenously with the serum, it appears rest- 

 less, lies on its belly, and respiration frequently increases; it 

 defecates frequently, finally falls upon its side, and commonly dies, 

 all within the space of two or three minutes. 



Serum Sickness in Man. Many observers have noted that the 

 injection of antitoxic sera into man sometimes is followed by a 

 fever, the appearance of a rash or urticaria, pains in the joints, etc. 

 In some individuals the reaction is shown after the first injection, 

 in most cases only after a second injection, given some time after 



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