788 THE ENDOCRINE ORGANS, OR DUCTLESS GLANDS 



stances in the blood other than epinephrine may not be responsible for 

 the cardiac changes. 



Of interest with regard to the action of epinephrine as part of a pro- 

 tective mechanism, is the fact that the contractile pigment cells pos- 

 sessed by certain types of lizards and whereby the hue of these creatures 

 is varied in accordance with the shade of the surroundings, are stimu- 

 lated by epinephrine ; the latter contracts such cells, and nervous excite- 

 ment in these animals has a similar influence (Redfield 32 ). It is scarcely 

 necessary to point out that, until it is definitely established by experi- 

 mental investigation that epinephrine may be discharged in excessive 

 amounts under certain conditions, it is irrational to assume that such may 

 occur in disease. The surgical removal of the adrenal gland is certainly not 

 warranted under any circumstances. 



The Association of the Adrenal with Other Endocrine Organs 



We have at present very little accurate and reliable information on the 

 association of the adrenal with other endocrine organs. That epinephrine 

 has an influence on many diverse organs and glands is an undoubted 

 fact, but this is more probably to be attributed to an activating influence 

 on sympathetic nerve endings than to any specific relationship between 

 the adrenal glands and the particular gland in question. The most impor- 

 tant of the results that have been obtained are the following : 



1. With the Thyroid and Parathyroid. Cannon and Cattell, after con- 

 firming Bradford's discovery that an electric current of action is set up in 

 the salivary gland when it is excited to activity, proceeded to investigate 

 the occurrence of such a current in the thyroid gland. 33 By placing one 

 nonpolarizable electrode on the gland itself and the other on the neigh- 

 boring subcutaneous tissues or on the trachea, a current was found to be 

 set up by stimulation of the sympathetic nerve supply of the thyroid, by 

 intravenous injection of epinephrine, or by stimulation of the great 

 splanchnic nerve before it reaches the adrenal gland. This last result, 

 which is the most important in the present connection, was, however, not 

 observed when the blood of the inferior vena cava was prevented by the 

 application of a clamp from getting to the heart, but immediately ap- 

 peared, after stimulation, when the clamp was removed. This experiment 

 taken alone does not, however, justify the conclusion that there is any 

 direct relationship between the adrenal glands and the thyroid, because 

 there are in the thyroid gland structures such as the muscle fibers in the 

 blood vessels, which a hypersecretion of epinephrine might affect. Before 

 any direct relationship between the two glands could be claimed to exist, 

 it would be necessary to show that the thyroid action current is obtained 

 with a concentration of epinephrine in the blood lower than that affecting 

 the blood vessels. 





