368 INFECTION AND RESISTANCE 



During the earlier periods of experimentation there was a 

 marked discrepancy in the ease with which guinea pigs could be 

 sensitized by American and German investigators, on the one hand, 

 and by Besredka and Steinhart in France, on the other. The mor- 

 tality, upon second injection, was much higher, with like quantities 

 of horse serum in the hands of the first-named. In attempting to 

 explain this, Rosenau and Anderson carried out typical experiments 

 with horse serum sent to them by Besredka and obtained high per- 

 centages of fatal results. They believe, for this reason, that the dif- 

 ferences cannot be accounted for by variations in the toxicity of the 

 horse sera, but conclude that probably there are varying grades of 

 susceptibility to the reaction in guinea pigs of different breeds. 



Next to guinea pigs the animals most commonly employed for 

 anaphylactic experiment are rabbits and dogs. In both of these the 

 symptoms and autopsy findings differ markedly from each other and 

 from those observed in guinea pigs. 



In sensitized rabbits the injection of a second dose of the antigen 

 is usually followed, after a short but definite incubation time, by 

 great weakness with, often, discharge of urine and feces. The ani- 

 mals sink down until the abdomen touches the ground, the legs are 

 stretched out weakly but not paralyzed, and the head may drop 

 forward or to one side. After this, the animal may gradually fall 

 upon its side and lie motionless except for labored and irregular 

 breathing and occasional twitching of the legs and head. Sometimes 

 this gradual relaxation may be interrupted by a sudden motor irri- 

 tation, the rabbit suddenly getting up and running a short distance 

 but soon falling down again apparently from a sudden return of the 

 muscular weakness. During these running spells it seems as though 

 there was no sense of direction or purpose the animals running into 

 obstructions or off tables as the case may be. During this period gen- 

 eral convulsions and a drawing back of the head by a tetanic spasm 

 of the muscles of the neck are not uncommon. Death may occur 

 within a few minutes, or it may follow a gradually increasing weak- 

 ness in the course of several hours. The fall of blood pressure here 

 seems to be purely secondary to the general failure of all the func- 

 tions. 26 



Anaphylaxis in dogs has been very extensively studied, especially 

 by Biedl and Ivraus, 27 and by Pearce and Eisenbrey. 28 The symp- 

 toms in dogs are characterized by a rapid progressive fall in the 

 blood pressure, followed by the symptoms of cerebral anemia. Ana- 

 phylactic dogs, after injection, will at first grow restless, vomit, and 



26 Arthus. Arch. Internal, de PhysioL, 7, 1909. 



27 Biedl and Kraus. LOG. cit.; also in "Kraus u. Levaditi Handbuch," 

 Erganzungsband 1. 



28 Pearce and Eisenbrey. Proc. Soc. Exp. Biol. and Med., 7, 1909, p. 30; 

 Transact. Congr. Am. Ph. and S. } Vol. 8, 1910. 



