744 THE ENDOCRINE ORGANS, OR DUCTLESS GLANDS 



nerve a rise in arterial blood pressure occurred provided the adrenal 

 veins were open, but not so if the adrenal veins were clamped. By re- 

 moving the viscera, the effect of splanchnic stimulation on the abdom- 

 inal blood vessels themselves is eliminated, and any constriction which 

 occurs in the blood vessels of the rest of the body must obviously be due 

 to the action of epinephrine. 



The most satisfactory of these methods is that more recently employed 

 by Stewart, Rogoff and Gibson, 69 which consists in observing the be- 

 havior of the pupil on the side from which the superior cervical ganglion 

 has been removed about one week previously. Of course the blood pres- 

 sure effect is also observed. 



Among the most important results secured by this method it may be 

 mentioned that dilatation of the pupil occurs on stimulation of the great 

 splanchnic nerve, provided the vena cava and adrenal vein are unobstructed 

 so that the blood from the adrenal glands can get to the head. If the vena 

 cava is clamped and the splanchnic nerve stimulated, there is no pupil- 

 lary dilatation, but it immediately occurs after the clamp is removed. 

 Epinephrine continues to be discharged for a considerable period of time 

 after stimulating the splanchnic nerve, but the immediate increase which 

 follows the application of the stimulus does not last long, so that more 

 secretion can be obtained by intermittent than by continuous stimula- 

 tion. It does not seem to be' possible to exhaust the adrenal gland of its 

 supply of active material by stimulating the splanchnic a fact which 

 would seem to throw considerable doubt on the reliability of the con- 

 clusions arrived at by the use of those methods in Avhich extracts of the 

 gland are assayed (see page 739).* 



Many interesting facts concerning the nature of the innervation of the 

 gland have been secured by one or other of the above methods. After 

 section of the sympathetic chain and the great splanchnic nerves on both 

 sides (in the thorax), no epinephrine is secreted into the blood of the 

 adrenal vein, and when one gland is extirpated and the nerve connec- 

 tions of the other entirely cut, the epinephrine content of the adrenal 

 vein blood sinks to not more than 1/1000 of the normal amount. The 

 animals survive this latter operation and behave in a perfectly normal 

 fashion, indicating that the internal secretion of the adrenals can not have 

 the physiologic significance so often ascribed to it. 



The splanchnic fibers concerned in the secretion of epinephrine seem 

 to come from a nerve center situated relatively low down in the spinal 

 cord. Section of the cord at the level of the last cervical segment does 

 not affect the spontaneous secretion, but this disappears when the section 

 is made beloAv the third thoracic segment. (Stewart and Rogoff.) 



"Another great advanlage of tl'e aufoinjection method is that no confusion can be caused by 

 the development of prcssor substances through clotting. 



