35 



In the case of 14 of the sensitized guinea pigs, the reinjection 

 was made intravenously, using 1 to 2 cc. of azoprotein ^) per 

 500 gram weight of the animals. 5 animals died within a few 

 minutes, 3 showed severe, 5 slight manifestations of anaphylactic 

 shock. Nine control animals showed no symptoms. 



Five animals treated in the manner described showed no ana- 

 phylactic reaction after the intravenous injection of azo-compounds 

 obtained by combination of tyrosin and p-arsanilic acid ; the injection 

 of azoprotein (fowl serum -\- p-arsanilic acid) made an hour later 

 failed to produce shock. As a control experiment, in 3 animals an 

 azo-compound of metanilic acid and tyrosin was used for the intra- 

 venous injection. These animals showed anaphylactic symptoms on the 

 subsequent injection of azoprotein (fowl serum -j- p-arsanilic acid). 



The results obtained demonstrate that guinea pigs previously 

 injected with an azoprotein (horse serum -|- arsanilic acid), show 

 anaphylactic reactions upon being reinjected with another azoprotein 

 containing the same group, i.e. fowl serum -\- arsanilic acid; but 

 they do not show such symptoms upon being reinjected with a 

 compound of arsanilic acid and a substance of simple composition, 

 i.e. tyrosin. The latter substance, on the other hand, seems capable 

 of desensitizing the animals. 



The Hague. Laboi^atory of the "R. K. Ziekenhuis" . 



^) Prepared as indicated in Biochem. Zeitschr. 86, p. 362. 



3* 



