262 PROTEIN POISONS 



so lowered that it no longer manifests itself in anaphylactic 

 shock when a reinjection is made. Moreover, in all instances 

 in which it has been tested, the refractory state is only 

 temporary, and sooner or later the sensitized condition is 

 sufficiently restored to be recognizable by anaphylactic 

 shock. We will take up this point again when we discuss 

 the theories of anaphylaxis. 



The Arthus Phenomenon. This phenomenon, already 

 referred to, deserves more detailed study. Arthus 1 observed 

 that a single injection of horse serum into rabbits, whether 

 the amount was small or large, whether the injection was 

 made subcutaneously, intraperitoneally, or intravenously, 

 whether the serum was unheated or heated to 57, had no 

 recognizable effect at the time or later, but that repeated 

 injections were followed by certain constant results. When 

 daily subcutaneous injections of 5 c.c. were made, the 

 following effects were observed: After the first three injec- 

 tions the serum was readily absorbed in a few hours; after 

 the fourth there appeared a soft infiltration about the 

 point and this disappeared after two or three days; after 

 the fifth the infiltration, which appeared, was hard, edema- 

 tous, and required five or six days for its absorption; after 

 the sixth there appeared a hard, compact, aseptic mass 

 which remained unchanged for weeks; after the seventh, 

 there was the same condition much accentuated. The 

 skin over the swelling became red, then whitish and dry; 

 the tissue became gangrenous and finally dropped out, 

 leaving a deep wound which slowly contracted into a scar. 

 This local reaction became more marked, and more extended, 

 with further repetitions of the injections. This reaction is 

 strictly specific, inasmuch as animals first treated with 

 horse serum do not react to subsequent treatment with 

 other sera or with milk. Subsequent studies show that 

 this reaction can be obtained in the same way in guinea- 

 pigs, rats, and pigeons. It is not necessary that the sensi- 

 tizing and the reinjections be made in the same way. If 



1 Compt. rend, de la Soc. biol., 1903, 817. 



