Abstract
1. We showed in a previous paper, by the blood pressure and eye reactions, that after section of the nerve supply of the adrenal no demonstrable liberation of epinephrin was present in cats as long as five weeks after the nerve section.
2. As it is easier to detect very small concentrations of epinephrin by the rabbit intestine and uterus segments, we have made a series of survival experiments in cats in which these tests were used to supplement the eye reactions. In all the animals one adrenal was excised and the nerves of the other cut.
In a cat tested two weeks after the operation, it was shown that the adrenal blood serum could not have contained 1:300,000,000, or the blood 1:400,000,000 of epinephrin; and that the rate of liberation of epinephrin could not have been at most 0.000001 mgm. per minute for one adrenal. In another cat three weeks after the operation the serum of the adrenal blood was proved to contain less than 1:400,000,000 and the blood less than 1:700,000,000 epinephrin. The output of epinephrin per minute could not have been as much as 0.0000009 mgm. per minute, for one adrenal. The segments used for the tests in these experiments were extremely sensitive, and the limits of adrenalin concentrations which could be detected with certainty were carefully determined. The eye reactions were negative. In these two cats the rate of liberation of epinephrin, if any liberation whatever was going on, must have been several hundred times less than the rate in normal animals under the same experimental conditions.
It is scarcely necessary to point out that experiments yielding completely negative results indicating the absence of epinephrin with very sensitive test objects are much more important for the questions studied than experiments in which small amounts of epinephrin can still be detected. For it is impossible to be certain that when a little epinephrin is found some of the fibers concerned in the liberation may not have escaped section.
3. Since these animals had completely recovered from the operation and behaved in every way like normal animals, it must be concluded that the liberation of epinephrin from the adrenals is not indispensable for life or health, unless indeed the necessary quantity is, even in the adrenal vein blood, below the limits of detection by the methods used. The epinephrin in the adrenal blood is diluted enormously (probably at least one hundred times) in the right heart; so that in these cats the concentration in the arterial blood could not, at most have reached 1:40,000,000,000 and 1:70,000,000,000, respectively.
If the liberation of epinephrin is totally abolished by division, in the dorsal cord, of the path concerned in it, as our experiments on the Relation of the Spinal Cord to the Spontaneous Liberation of Epinephrin indicate, this corroborates the conclusion that epinephrin is not indispensable, since numerous animals and men have long survived such lesions.
4. The experiments indicate that the entire liberation of epinephrin from the adrenals is controlled by nerves.
5. In some of the other cats the residual output of epinephrin was so small that it was doubtful whether it was being liberated at all in detectable amount. In all, the rate of liberation, even where a definite output could still be detected, was reduced to a small fraction of the normal.
6. In a number of acute experiments on cats and dogs, the reduction in the output of epinephrin after section of the various possible nerve paths to the adrenals was studied. In all, epinephrin was still found in detectable amount in the blood coming from the adrenals, although the rate of liberation was reduced to a small fraction of the initial amount.
Footnotes
- Received May 12, 1917.
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