THE ADRENAL GLANDS 743 



noted (Fig. 192). If the fluid added to the inflowing fluid contains epi- 

 nephrine, the outflow will become diminished. This is a very satisfactory 

 method, although it is somewhat limited in scope unless large frogs are 

 procurable, because of the difficulty of getting the necessary cannulas 

 into the vessels (aorta and abdominal vein). 



5. The pupil of the enucleated eye of the frog. Extremely small traces 

 of epinephrine are observed to cause a dilatation. 



6. The denervated iris. The fluid to be tested is placed in the conjunc- 

 tival sac of an animal from which the superior cervical ganglion of the 

 corresponding side has been removed some days previously. Under such 

 conditions, if epinephrine is present in the fluid, dilatation of the pupil 

 occurs. Both of the preceding reactions we owe to Meltzer. 70 



It should be emphasized that, although each of these methods is in 

 itself very sensitive for the detection of epinephrine without being al- 

 ways specific, yet the result should not be considered conclusive unless 

 definite effects have been secured by at least two methods that are as 

 far as possible independent of each other. 



As an outcome of investigations by these methods it has been found 

 that, when blood from the adrenal vein is collected in a pocket of vena 

 cava made by applying clamps above and below the entrance of the 

 adrenal veins, the presence of epinephrine can be revealed, the rate of 

 secretion being from 0.0003 to 0.001 mg. per kilogram of body weight 

 per minute (Stewart and Rogoff). The absolute amount of epinephrine 

 liberated from the gland can be measured only by finding the concen- 

 tration in the adrenal vein blood and the rate of bloodflow. This amount 

 is approximately constant, so that the concentration in the blood which 

 collects in the cava pocket varies inversely with the rate of bloodflow. 

 In asphyxia the bloodflow is decreased so that the concentration of epi- 

 nephrine increases, but there is no change in the absolute amount. Nei- 

 ther anesthesia nor trauma affects the amount. The concentration is 

 likely to rise late in an experiment because of the slowing of bloodflow. 

 Adrenal activity may, however, be excited by massage of the gland, or 

 by stimulation of its nerve supply through the great splanchnic nerve. 

 The presence of epinephrine in blood collected directly from the adrenal 

 veins does not justify us in concluding that, when mixed with the re- 

 mainder of the blood in the body, there would be a sufficient concentra- 

 tion of this substance to develop any of its activities. It has therefore 

 been necessary to devise methods by which this possibility could be 

 tested. 



The Autoinjection Method. Such a method was first of all success- 

 fully used by Asher, who employed an animal from which all the abdom- 

 inal viscera had been removed. On stimulation of the great splanchnic 



