PHYSIOLOGY OF EPINEPHRINE 111 



functions of the medullary and cortical tissues in the mammal. 

 Ontogenetically and phylogenetically one finds an intimacy 

 which can not be dismissed as a mere vagary of nature. The 

 peculiar circulatory system of the adrenals by which, as we 

 have seen (Chapter II), the vessels from the cortex continue 

 into the medulla is further anatomical evidence for suspecting 

 some relation between the medulla and the product of the 

 cortex. The peculiar chemical properties of epinephrine in 

 its oxidation-reduction potentialities would render it ideal as 

 a protective agent for the vital and destructible cortical 

 hormone. Has epinephrine, therefore, in the mammal some 

 function which links it to the adrenal cortical hormone? Does 

 our ignorance of the function of the latter shroud also that of 

 epinephrine? 



The view that the function of epinephrine is to protect or 

 otherwise act synergistically with the adrenal cortical hormone 

 is supported by several other important facts. Sjostrand 578 

 found that those agents which cause an increased output of 

 epinephrine from the adrenals also increase the blood flow 

 through the cortex. This finding led him to suggest that 

 epinephrine was linked functionally with the activity of the 

 cortex. As we shall see later, the agents which stimulate 

 epinephrine secretion are also those which stimulate the 

 utilization and hence the demand for the cortical hormone. 

 One would thus be justified in concluding that the observed 

 stimulation of epinephrine which we have described as occurring 

 under various conditions is in reality only secondary to the 

 increased secretion of the cortical hormone which these con- 

 ditions call forth. 



If the theory outlined above is valid one must conclude 

 that in the mammal only the medulla is of functional sig- 

 nificance. The extra-medullary tissue is of little or no use- 

 fulness and merely a remnant of its occurrence in the lower 

 animals. That the extra-adrenal chromaphil tissue is of little 

 function in the organism as demanded by this hypothesis is 



