ADRENALS 655 



been brought forward by Asher and Flack. They compared the excita- 

 bility of the depressor nerve, and also the effect on the blood-pressure 

 of the intravenous injection of adrenalin, before and during stimulation 

 of the thyroid nerves. They conclude that, when all the other con- 

 ditions remain unchanged, both the effect of excitation of the depressor 

 and the effect of adrenalin are greater during stimulation of the thyroid 

 nerves than shortly before it without such stimulation. The difference 

 is really connected with the internal secretion of the thyroid, since it is 

 not obtained if the thyroids are previously extirpated, and injection 

 of thyroid extracts influences the resxilt exactly in the same way as 

 stimulation of the thyroid nerves. Similar indirect evidence has been 

 obtained by other observers (Oswald, Levy). 



Adrenal Bodies. It had been observed by Addison that the 

 malady which now bears his name, and in which certain vascular 

 changes, with muscular weakness, anaemia, and pigmentation or 

 ' bronzing ' of the skin, are prominent symptoms, was associated 

 with disease, usually tuberculous, of the adrenal bodies, commonly 

 called in human anatomy the ' suprarenal capsules.' This clinical 

 result was soon supplemented by the discovery that extirpation of 

 the adrenals in animals is incompatible with life (Brown-Sequard). 

 Our knowledge of the functions of these hitherto enigmatic organs 

 was extended by the experiments of Oliver and Schafer, who in- 

 vestigated the action of extracts of the adrenals (of calf, sheep, 

 dog, guinea-pig, and man) when injected into the veins of animals. 

 The arteries are greatly contracted, and this mainly through dirert 

 vaso-motor nerve-endings or some structure inter- 

 ^n t h ^m and the smooth mmrle of tbp vessels, but 



u^h the vaso-motor centre. The blood-pressure rises 

 rapidiyT^Ttliough the heart may be inhibited through the vagus 

 centre. The heart is at the same time directly stimulated, so that, 

 although it beats slowly, the beats are stronger than before. When 

 the vagi are cut the action of the heart is markedly augmented, 

 and the arterial pressure rises enormously (it may be to four or five 

 times its original amount) . Stimulation of the depressor is of no avail 

 in combating this increase of blood-pressure. The generalization 

 may be made that the active principle of the medulla epinephrin 

 or suprarenin, also called adrenin* acts upon all plain muscle 

 and gland-cells that are supplied with sympathetic nerve-fibres, and 

 the result of the action, whether augmentation or inhibition, is the 

 same as would be produced by stimulation of the sympathetic fibres 

 going to the muscle or gland in question. Yet it is not through 

 excitation of these fibres that epinephrin acts, for its effect is even 

 more pronounced when the nerve-fibres have been caused to de- 

 generate, in the case of the pupillo-dilator fibres, e.g., by excision 

 of the superior cervical ganglion. Nor is the effect a direct one on 



* It is advisable to restrict the term ' adrenalin ' 'to the well-known com- 

 mercial preparation of the active substance. 



