150 BACTERIOLOGY FOR NURSES 



ANAPHYLAXIS 



Ordinarily when an animal is given repeated injections of an 

 antigenic substance, the antibodies produced by the first injection 

 are increased and eventually a high degree of immunity is es- 

 tablished. Under certain circumstances, however, the reverse 

 seems to be the case. A second injection will produce severe and 

 even fatal symptoms, so that it would seem instead of immunity 

 a state of hypersusceptibility or hypersensitivene.^s has been pro- 

 duced. 



To this state of hypersusceptibility Richet gave the name 

 anaphylaxis, meaning " without protection," because to him it 

 represented the reverse of prophylaxis. Recent researches, how- 

 ever, tend to show that the two conditions may not be opposed, 

 but may even be closely related. The term " allergy " or " altered 

 energy " has been suggested as a more appropriate one. 



According to the theory of Vaughan the phenomenon of ana- 

 phylaxis may be explained by supposing that when a protein such 

 as horse serum or egg albumin or bacteria is injected it is broken 

 up'by an enzyme present in small amounts in the body into a toxic 

 and a non-toxic portion. At the first injection the disintegra- 

 tion takes place slowly and the body is slightly or not at all affected. 

 By the second time the injection is given, however, considerably 

 larger quantities of the splitting enzyme have been elaborated, 

 so that a large amount of the toxic portion is immediately liberated 

 and symptoms quickly appear. The second injection causes no 

 symptoms unless, as in all immunity reactions, sufficient time is 

 allowed to elapse for the cells to combine with the proteins and for 

 the specific ferments to be produced. The exact nature of the re- 

 action is as yet unknown. Recent research tends rather to support 

 the view that anaphylaxis occurs as a result of the union between 

 antigen and antibody, taking place in the body cells and not in the 

 blood stream. Further work may reveal that both factors are 

 concerned. 



Experimental anaphylaxis in animals shows that the first 

 injection of a foreign protein which in itself is not poisonous so 



