436 THE POPULAR SCIENCE MONTHLY 



The period of incubation, however, may be shortened if an animal 

 is rendered passively anaphylactic. This process depends upon the 

 fundamental observation of Gay and Southard that a normal guinea-pig 

 may be sensitized by injecting it with the serum of another guinea-pig 

 which is already sensitized. If a normal guinea-pig is thus injected 

 with the serum of an animal (guinea-pig, or rabbit more usually) 

 which was sensitized some weeks previously, this normal guinea-pig 

 becomes fully sensitized within twenty-four hours and will respond with 

 typical symptoms when injected with the same proteid which was used 

 to sensitize the donor of the serum (Otto). The serum of an actively 

 sensitized animal, that is, one sensitized by the injection of a foreign 

 proteid, therefore contains some substance, termed a serum-rest or 

 anaphylactin by Gay and Southard, which upon injection fully sensi- 

 tizes a normal animal within a few hours. 



Intoxication. — In this stage we observe how a sensitized animal 

 responds with violent symptoms to an injection of the same proteid 

 which it formerly tolerated with no apparent ill effect; we see the 

 remarkable transformation of what formerly was an apparently harm- 

 less substance into a violent poison. The symptoms and signs notice- 

 able in an animal during this stage vary with the species and with the 

 site of injection of the toxic dose. If the injection is given subcutane- 

 ously in rabbits, an area of edema develops in the place injected; this 

 edema may gradually lead to a circumscribed necrosis of the skin 

 (phenomenon of Arthus). The same change may also occur in guinea- 

 pigs, as Lewis has shown. If the second injection is given intraven- 

 ously in rabbits, a more or less marked respiratory disturbance asso- 

 ciated with muscular weakness and increased peristalsis develops 

 (Arthus) ; if the rabbits are highly sensitized, convulsions followed by 

 death occur in a few minutes (Arthus). In the dog, the respiratory 

 symptoms are not prominent, but the animal shows nausea and vomit- 

 ing, profound muscular weakness and often discharge of urine and 

 feces. The animals, however, usually recover. In the guinea-pig, the 

 stage of intoxication is dominated by respiratory symptoms. The 

 animal makes such powerful respiratory attempts that the costal arch 

 is drawn inwards with each inspiration; these efforts swiftly become 

 convulsive and the animal dies a few minutes after the intravenous 

 injection of an adequate dose (Auer and Lewis). 



Anatomical and Functional Changes Found in the Stage of Intoxi- 

 cation. — The study of anaphylaxis from the clinical symptoms alone is 

 unsatisfactory. The symptoms offer nothing which could not be pro- 

 duced by numerous drugs available to the investigator; they do not 

 indicate why the animal shows these disturbances. For an adequate 

 picture of the process the seat of these reactions and a finer analysis of 

 the functional disturbances is necessary. Moreover, no rational thera- 



