THE ADRENAL GLANDS 745 



In connection with these observations it is of interest to note that dur- 

 ing stimulation of the splanchnic nerve in a normal animal, the conse- 

 quent rise in blood pressure shows two peaks (see Fig. 29, page 137). The 

 first is no doubt due to direct stimulation of the splanchnic vasoconstric- 

 tors, and the second to the outpouring of epinephrine into the blood, the 

 justification for this conclusion being that the latter rise fails to appear 

 after removal of the adrenal glands. 



Taking the results as a whole, it is indeed doubtful whether under nor- 

 mal conditions a sufficient amount of epinephrine is discharged into the 

 blood of the vena cava to affect appreciably the tone of the blood vessels, 

 and this conclusion seems all the more justified because of the fact that 

 .small quantities of epinephrine have a dilating rather than a constricting 

 influence, at least on certain vessels (Hartman 6 ' 4 ). It may be, however, that 

 the maintenance of vascular tone under certain conditions is greatly as- 

 sisted by the presence of epinephrine in the blood. Similarly the sympa- 

 thetic control of other functions may be facilitated by the presence of 

 small amounts. It has been found, for example, that, although stimula- 

 tion of the celiac plexus causes the glycogen stored in the liver to be con- 

 verted into sugar, this result is not as a rule obtained on stimulating 

 the plexus shortly after removal of the adrenal glands. The presence 

 of epinephrine in the blood would, therefore, seem to be necessary to bring 

 about functional activity of the sympathetic nerve endings concerned in 

 the glycogenolytic process (see page 637). 



Adrenalemia. In the light of these researches it is important to point 

 out that a great part of the work done by clinical observers purporting to 

 show that in such conditions as nephritis and arteriosclerosis there is an 

 increase of epinephrine in the blood, has been found by Stewart and 

 others, using controlled methods, to be entirely uiiproven. 70 Some inves- 

 tigators, however, still hold that temporary conditions, such as transient 

 rises of arterial blood pressure or temporary glycosuria, may sometimes be 

 due to increased adrenal discharge into the blood. 



Ephinephrine has been thought to be a substance which is secreted into 

 the blood in supernormal amount when certain emergencies arise, the most 

 important of these being fright, or some other extreme emotion. This 

 belief has arisen partly from the similarity in the general behavior 

 of an animal following the intravenous injection of epinephrine and dur- 

 ing states of extreme excitement. Dilatation of the pupils, bristling of 

 the hair, salivation, rise in arterial blood pressure, inhibition of the intes- 

 tinal movements, protrusion of the eyeballs are all symptoms of fear just as 

 they are of epinephrine injection. Impressed by these resemblances Can- 

 noii 72 undertook an extended research to test the hypothesis that the reac- 

 tion of an animal to fear and other emotional states is partly dependent on 



