Histamine Reactions in Isolated Canine Tissues 183 



is therefore not only the dominant but the essential reacting 

 organ in canine anaphylactic shock. 



2. Canine peptone shock. The severity of the peptone reac- 

 tion is reduced in dehepatized dogs, and is further reduced in 

 completely eviscerated dogs. There are therefore important 

 though not dominant hepatic and intestinal factors in this shock. 

 In dehepatized dogs, recover}' from the shock does not take 

 place, the animals dying in about 60 minutes. The liver, there- 

 fore is the essential or dominant organ in peptone recovery. 



3. Canine histamine shock. The severity of the histamine 

 reaction is not reduced in dehepatized dogs nor in eviscerated 

 dogs. The dominant reacting tissues in this shock, therefore, 

 are either confined to the extra-hepatic and extra-intestinal 

 parts, or are fairly evenly distributed throughout the body as 

 a whole. Recovery from histamine shock takes place as prompt- 

 ly and completely in dehepatized and eviscerated dogs as in in- 

 tact animals. 



Canine anaphylactic, peptone and histamine shock, therefore, 

 are not physiologically identical reactions, at least in so far as 

 their initial or fundamental physiologic mechanisms are con- 

 cerned. The secondary reactions due to low systematic blood 

 pressure are presumably identical in the three shocks. In the 

 later stages of each shock, the secondary reactions conceivably 

 dominate the clinical picture. 



87 (2047) 



Histamine reactions in isolated canine tissues. 



By W. H. MANWARING, R. E. MONACO, and H. D. MARINO. 



[From the Laboratory of Experimental Pathology, Stanford Uni- 

 versity, California.] 



Marked histamine reactions may be demonstrated by perfu- 

 sion methods in isolated canine organs. The following are the 

 reactions thus far studied : 



1. Isolated hind-quarters. Distinct decrease in perfusion re- 

 sistance (vasodilation), increasing the rate of perfusion flow 

 from 15 per cent, to 200 per cent, depending upon the initial 



