SECRETION OF THE DUCTLESS GLANDS. 887 



have not been entirely satisfactory; some claim to have shown its 

 presence, while others get negative results. It is generally believed, 

 however, that the blood does receive constantly a supply of epi- 

 nephrin from the adrenal glands and that this constitutes the inter- 

 nal secretion of the medullary cells. As regards the function of the 

 epinephrin under normal conditions there is some difference of 

 opinion. The usual view is that it serves to maintain a condition 

 of tonicity in the musculature of the heart and blood-vessels inner- 

 vated by the sympathetic autonomic system and thus insures a 

 normal cardiovascular tone. If the amount of epinephrin falls 

 below normal or fails entirely, a condition of hypotension results in 

 consequence of general vascular dilatation. When epinephrin is 

 secreted in excess the opposite condition of hypertension prevails. 

 This theory is not accepted by some of the workers in this field.* 

 They state that experimental injections of epinephrin in concen- 

 trations equivalent to those that may be considered normal in the 

 blood, cause a lowering of pressure rather than an increase, possibly 

 because in such low dosage it acts upon the vasodilators rather than 

 the vasoconstrictors. In the second place complete removal of the 

 adrenal bodies is not followed by a prompt loss of vascular tone as 

 might be expected on the theory given above. An alternative or 

 supplementary theory that has been proposed is that the secretion 

 of epinephrin constitutes a reserve mechanism that comes into ac- 

 tion at times of stress. Under the emotional excitement at such 

 times there is a reflex excitation of the sympathetic autonomic sys- 

 tem, including the nerve supply to the adrenal glands. The in- 

 creased secretion of epinephrin thus produced is of benefit in that 

 it facilitates or augments the response of the sympathetic nerves, 

 giving a more rapid heart-beat, a greater flow of blood to the mus- 

 cles, central nervous system, and heart, and also by increasing the 

 output of sugar from the liver, f In spite of the large amount of 

 experimental work upon the action of epinephrin, it seems neces- 

 sary at present to recognize the fact that our knowledge is too 

 incomplete to justify any positive statements in regard to its 

 normal role in the organism. 



As stated above, the rise of blood-pressure and the slow heart- 

 beat caused by injections of epinephrin last but a few minutes. 

 Apparently the excess above the normal concentration in the blood 

 is quickly destroyed in some way. Possibly it is absorbed and oxi- 

 dized or otherwise changed by the tissues, but on this point also 

 experiments as yet have not given a decisive result. { 



The Functional Significance of the Cortical Tissue. Most ob- 



* Hoskins and McClure, "Archives of Internal Medicine," 10, 343, 1912. 



t See Cannon, "American Journal of Psychology," 25, 256, 1914. 



t For general reviews of literature, consult Biedl, "Innere Sekretion," 1913. 



