THE ADRENAL GLANDS 785 



(page 784). It was found that after the pocket had been allowed to fill 

 with blood removal of the upper clamp caused the pupil to dilate. Fur- 

 thermore, the latent period of the response coincided with the time which 

 the wave of concentrated blood was calculated to take in traveling from 

 the pocket to the eye. This reaction time, consequently, varied inversely 

 with the rate of blood flow. Stimulation of the splanchnics or massage of 

 the gland was without effect upon the pupil so long as the upper clamp 

 remained in position, but the usual response ensued when the clamp was 

 removed.* 



When the adrenals were not artificially excited in any way the con- 

 tents of the pocket, after removal of the upper clamp produced the char- 

 acteristic reaction upon the pupil, thus demonstrating the spontaneous 

 liberation of epinephrine from the glands. The capacity of the pocket, 

 together with its time of filling, having been determined, the rate of 

 flow through the adrenal veins was readily arrived at. The degree of 

 concentration of the pocketed blood was determined indirectly by noting 

 the precise extent of the pupillary response following the removal of 

 the upper clamp, and subsequently reproducing this reaction by the intra- 

 venous injection of an equal quantity of epinephrine solution of known 

 concentration. It is clear that the product of the rate of blood-flow 

 through the veins and the degree of concentration in epinephrine of the 

 blood in the pocket will give the amount of epinephrine liberated from the 

 glands in a given time. This was found to vary between .0003 and .001 

 mg. per kilo of body weight per minute. 



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 sec- 

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



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

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

 quent rise in blood pressure shows two peaks (see Fig. 29, p. 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. In many cases a well-marked 

 "dip" is seen between the two rises. This is explained as being due to 

 initial minute amounts of epinephrine passing into the blood streamf (see 

 page 777). 



*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 relia- 

 bility of the conclusions arrived at by the use of those methods in which extracts of the gland are 

 assayed (see page 779). 



tA 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 Rogoff to be unproved. 



