302 



ALFRED C. REDFIELD 



TABLE 1 



Per cent of sugar in blood of horned toads 



It is clear that the sugar content of the blood in those animals 

 which had undergone nervous excitement is higher than in the 

 normal animals, but not as high as in animals into which adrenin 

 has been injected. The conclusion is warranted that the horned 

 toad exhibits an emotional hyperglycemia, which indicates 

 that adrenin is secreted into the blood stream during nervous 

 excitement. 



Although a number of very sensitive tests for adrenin are 

 known, no one, according to Stewart ('12), has succeeded in 

 demonstrating the presence of adrenin in the general circulation 

 of mammals. In the hope that the adrenal secretion of the 

 horned toad might be greater than that of mammals, an attempt 

 has been made to detect adrenin in the blood of these animals 

 during states of nervous excitement. The method devised by 

 Cannon and de la Paz ('11) was finally selected for this purpose. 

 This test depends upon the inhibition of the rhythmic contrac- 

 tions of the longitudinal muscles of the intestine by minute 

 quantities of adrenin. The method was successfully modified so 

 that adrenin could be detected at dilutions of one part in ten 

 million, and in quantities of blood so small as 0.7 cc. Although 

 a number of positive tests for adrenin were obtained from blood 

 from excited horned toads, the majority of the results were so 

 variable that no weight can be placed upon the experiments. 

 The difficulty which must attend the detection of adrenin in the 

 circulation prevents this negative evidence from having any effect 

 upon the hypothesis developed in this paper. 



If adrenin is produced in the circulation of the horned toad dur- 

 ing nervous excitement and is responsible for the contraction of 



