PASSIVE ANAPHYLAXIS 559 



of fibrin. Thus stimulated, the cells pour out an unusual amount of 

 antithrombin. On account of the consumption of a part of the fibrino- 

 gen and the increased formation of antithrombin the blood fails to coagu- 

 late after anaphylactic shock or peptone poisoning. Owing to the 

 coagulation deposits on the endothelial cells, the viscidity is increased 

 and the leukocytes adhere to the vessel-walls, thus accounting for the 

 leukopenia observed after protein injection. The endothelial cells are 

 injured, and the walls of the capillaries become more readily permeable, 

 thus accounting for the local edema often seen in anaphylaxis. The 

 fine capillaries of a given area may be occluded by thrombi, thus ex- 

 plaining the necrosis characteristic of the Arthus phenomenon. The 

 irritation of the endothelial cells extends to the smooth muscle, leading 

 to vasoparalysis and the characteristic fall in blood-pressure. The 

 affinity of the endothelial cells for the protein is stimulated by the first 

 injection, and acts in a fulminating way on reinjection, thus explaining 

 the suddenness of anaphylactic shock. 



The theory, therefore, also assumes the formation of a ferment that 

 acts primarily upon the proteins of the blood, leading to the formation 

 of fibrin, which, as it were, mechanically induces the lesions and symptoms 

 of anaphylaxis. While it offers a plausible explanation, the theory is 

 not well supported, and at best may be regarded as a modification of 

 Vaughan's theory, demonstrating one way in which the protein poison 

 may act. 



PASSIVE ANAPHYLAXIS 



Passive anaphylaxis is produced by the injection of normal animals 

 with the blood or serum of animals or persons already sensitized. It 

 is similar to passive immunization, and is specific for the anaphylactogen 

 with which the donor is sensitized. 



The second animal may be of the same or of another species. If 

 it is of the same species, the condition induced by the transference of 

 the serum is called homologous; if it is of a different species, it is known 

 as heterologous, or passive anaphylaxis. 



Passive anaphylaxis was discovered almost simultaneously and in- 

 dependently by Gay and Southard, 1 working with guinea-pigs, by 

 Nicolle, 2 with rabbits, and by Otto, 3 who, working with both guinea-pigs 

 and rabbits, showed that a rabbit immune serum would passively sensi- 

 tize a guinea-pig. 



1 Jour. Med. Research, 1907, xvi., 143. 2 Ann. de 1'Inst. Pasteur, 1907, xxi, 128. 

 3 Munch, med. Wochenschr., 1907, No. 39. 



