Chapter VI 



THE PHYSIOLOGY OF THE ADRENAL MEDULLA 



No product of the glands of internal secretion has been 

 studied with such thoroughness as has been epinephrine. This 

 intense study has been made possible by the fact that this 

 substance can be detected and assayed in extremely minute 

 concentrations. It has thus been possible to determine the rate 

 of secretion of epinephrine under various conditions. The 

 results of these studies shall be considered in the present chap- 

 ter with particular reference to their bearing on the functional 

 significance of epinephrine in the organism. 



Epinephrine manifests its presence, even in extremely dilute 

 solution, by a number of pharmacological reactions. These 

 have been utilized for determining the concentration of epi- 

 nephrine present in the blood leaving the adrenals. Despite 

 their apparent simplicity and great sensitivity, the methods used 

 in the study of epinephrine secretion are open to a number of 

 criticisms particularly as regards the physiological significance 

 of the data obtained. It is not surprising, therefore, that 

 authors, utilizing different techniques, have obtained conflict- 

 ing data and come to diametrically opposed conclusions as 

 regards the significance of their results. In order to evaluate 

 properly the existent data it is necessary to consider first the 

 various methods utilized for determining the rate of epi- 

 nephrine discharge from the adrenals. 



For determining the rate of discharge of epinephrine from 

 the adrenals at any given time, it is obviously necessary to 

 know the concentration of epinephrine in the blood of the 

 adrenal veins and the amount of blood leaving the glands in 

 unit time. 525 Many of the earlier workers, unfortunately, 

 neglected to take the last factor into consideration, assuming 



87 



