784 THE ENDOCRINE ORGANS, OR DUCTLESS GLANDS 



noted (Fig. 194). 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 cannulae 

 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 methods we owe to Meltzer. 22 



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 was taken from the inferior vena cava at the level of the adrenal 

 veins, i. e., blood with a relatively high concentration of adrenal secretion, 

 the presence of epinephrine could be revealed after splanchnic stimulation 

 or massage of the glands. Such methods which depend upon the removal 

 from the animal of the blood to be tested, are open to the objection that the 

 blood so obtained may become altered in the process of shedding or defib- 

 rination. As a matter of fact it has been shown that shed blood, very rap- 

 idly develops vasoconstrictor substances. On this account conclusions re- 

 garding epinephrine content, based upon the behavior of such samples, are 

 not wholly reliable. The method about to be described is preferable. 



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 

 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 modification of this method is that employed more 

 recently by Stewart, Kogoff and Gibson. 23 Blood from the adrenals was col- 

 lected in a pocket of the inferior vena cava, which was made by applying 

 clamps to this vein above and below the level of the adrenal veins. An 

 animal in which the iris had been sensitized towards the action of epineph- 

 rine by prior removal of the superior cervical ganglion was employed 



