HYPERSENSITIVENESS 481 



and Siinoiids (1923, 1925) noted definite changes in ])ern)ea- 

 ])ility which Manwaring regards as characteristic of anaphylaxis 

 in the dog. 



In Manwaring's opinion, the explosive liberation of a toxin by 

 the liver is responsible for canine anaphylactic shock. Simonds 

 (1923) and Simonds and Brandes (1924) have offered a different 

 explanation of the hepatic phenomena. They find that the walls 

 of the hepatic veins contain a large amount of nonstriated mus- 

 cle. They conclude from their experimental work that the drop 

 in blood pressure and the engorgement of the liver observed in 

 canine anai^hylaxis result from increased pressure in the hepatic 

 veins caused by tlie tetanic contraction of the smooth muscle 

 present in the vessel walls. 



Sherwood and Stoland reported that while animals injected 

 with horse serum showed increased permeability changes, the 

 phenomenon is observed in animals tliat have not become sen- 

 sitized to horse serum; it can be demonstrated by perfusion with 

 Locke's solution without antigen and is present in desensitized 

 animals. The chronaxie studies of Stoland, Sherwood, and Wood- 

 bury (1931) indicate that following the injection of horse serum 

 there develops an increase in irritability of the vagus which cor- 

 relates with increased permeability of the tissues but does not 

 always indicate that the animal is sensitive. They note also, that 

 about 10 per cent of the sensitized dogs show no prolongation 

 in the clotting time of the blood during shock. When the clotting 

 time is prolonged, it is due, according to Stoland and Haughey 

 (1932), to the liberation of a heparin-like substance by the liver. 

 The role of heparin as a factor in blood coagulation has been 

 studied extensively by Howell and Holt (1918) and more re- 

 cently by Howell (1924). 



Anaphylaxis in the Cat. — In 1900 Brodie called attention to 

 the extreme sensitivity of normal cats to natural foreign proteins 

 administered intravenously. Doses of foreign blood serum, egg 

 white, etc., that are entirely nontoxic for guinea pigs, rabbits, 

 dogs and other animals, caused a marked fall in arterial blood 

 pressure in the normal anesthetized cat. For this reason, Man- 

 waring (1910), Schultz (1911), Edmunds (1914), and later 

 Drinker and Bronfenbrenner (1924) have encountered difficulty 



