212 Thyroid and Adrenal 
~in the experiments with Laewen-Trendelenburg frog or rabbit 
heart, the action of epinephrine was augmented by the addition 
of thyroid extract. In the same manner, the plasma of rats fed 
on thyroid and plasma obtained from patients with Graves’ dis- 
ease, had a well marked accelerating action on vasoconstrictor 
influence of epinephrine. Asher considers that thyreoglandol, | 
which is protein-free and practically iodine-free, exerts the same 
biological and metabolic action as the whole gland. Levy" re- 
ported that in ordinary and adrenalectomized cats stimulation 
of the cervical sympathetic nerve can increase the effectiveness 
of epinephrine in raising arterial pressure, although this is not the 
case in thyroidectomized cats. He concluded that thyroid secre- 
tion renders more excitable the sympathetic structures acted on 
by epinephrine in raising arterial pressure, and the increased 
effectiveness of epinephrine as a pressor agent after thyroid 
stimulation is not dependent on a greater amount of circulating 
epinephrine. On the other hand, however, he and Cannon and 
Cattell’? obtained some evidence indicating that stimulation of 
the cervical sympathetic nerve or epinephrine injection induces 
secretory activity in the thyroid gland. In my previous experi- 
ments,! when epinephrine was injected into thyroid-fed rabbits, 
epinephrine glycosuria was induced to the same extent as in con- 
tro] animals; the hyperglycemia being practically the same or 
somewhat augmented. 
w 
SUMMARY. 
The epinephrine content of the adrenals of normal medium 
sized albino rats is 2.2 mg. per gm. of the gland. Comparing 
this figure with those reported by other investigators with larger 
animals, the epinephrine content of rat adrenal is the nearest to 
that of the dog, larger than that of the cat, and smaller than 
that of the sheep and calf. Thyroid feeding of either short dura- 
tion with large doses or long duration with small doses does not 
materially change the epinephrine content, nor the weight of the 
adrenals of medium sized albino rats. If hypersecretion of the 
adrenals really exists in experimental hyperthyroidism, these 
16 Levy, R. L., Am. J. Physiol., 1916, xli, 492. 
17 Cannon, W. B., and Cattell, McK., Am. J. Physiol., 1916, xli, 74. 
