MECHANISM OF ANAPHYLAXIS 541 



to horse serum, as was shown by Schultz and Jordan. This reaction is 

 evidenced by restlessness, marked irritability of the skin, involuntary 

 passage of urine and feces, and temperature and blood-pressure changes. 

 Anaphylactic reactions have also been observed to occur in numerous 

 other animals, e. g., in cows, sheep, horses, hens, pigeons, and in 

 certain cold-blooded animals, the symptoms varying according to the 

 species. These reactions have not as yet been carefully studied. 



MECHANISM OF ANAPHYLAXIS 



Whereas the lesions and symptoms of anaphylactic shock here 

 described in different species of animals are those commonly observed 

 with serum proteins, they vary in no essential when any protein agent 

 is used when the conditions of dosage and administration are the same. 

 It is evident, however, that no one symptom, or group of symptoms, 

 can be regarded as characteristic of anaphylaxis in all animals. The 

 various species present widely differing pictures with the same protein 

 substance, and these differences are best explained on the ground of 

 changes in the anatomic structure and physiologic reaction of different 

 animals. Thus, Schultz has shown that serum anaphylaxis is essentially 

 a matter of hypersensitization of smooth muscle in general, and that, 

 during anaphylactic shock, all smooth muscle contracts. In the guinea- 

 pig this effect is. most evident in the bronchi, owing to the peculiar, 

 though normal, anatomic structure of the mucosa, which is relatively 

 thick as compared with the lumen, so that contraction of the smooth 

 muscle throws it into folds that completely occlude the bronchi causing 

 death from inspiratory asphyxia. The bronchial mucosa of dogs, 

 rabbits, and rats, however, is relatively thin and poor in smooth muscle 

 tissue, which may account for an entire absence of transitory respiratory 

 difficulties during anaphylactic shock in these animals. In the dog the 

 most marked effect is apparent upon the smooth muscle of the gastro- 

 intestinal tract, contraction resulting in setting up vigorous intestinal 

 peristalsis, vomiting, and involuntary emptying of the urinary bladder. 

 The characteristic initial rise in blood-pressure may be due to con- 

 striction of the splanchnic, pulmonary, coronary, and systemic arteries, 

 followed by a condition of paresis and a fall in blood-pressure. The 

 cardiac muscle is also involved, particularly on the right side, as shown 

 by Robinson and Auer, and this favors a venous accumulation of blood. 

 In the rabbit a similar effect is noted upon the smooth muscle of the 

 blood-vessels, and particularly on the heart, as well as upon the gastro- 



