THE SUPRARENAL SYSTEM 267 



excitability of the sympathetic system, especially in so far as they 

 make themselves felt in the periphery, are associated with varia- 

 tions in the activity of the adrenal system. 



That the maintenance of tone by the sympathetic system in 

 the cardiac and vascular muscles is an important factor in the 

 normal circulation of the blood, has long been known and has 

 been duly appreciated. A far-reaching significance is also attach- 

 ing to the tonic innervation of all vegetative organs, this tone 

 being maintained, partly by stimulation, and partly by inhibition, 

 on the part of the sympathetic system. The sympathetic also 

 regulates the sugar contents of the blood, and in this way exer- 

 cises a determining influence upon the metabolism of the carbo- 

 hydrates, which plays so important a part in normal muscular 

 exertion. It seems probable from recent observations that the 

 metabolism of albumin and of salt, as well as the composition of 

 the blood, undergo a certain degree of modification by the. agency 

 of the sympathetic. Seeing that adrenalin is the hormone by 

 which the irritability of the sympathetic system is regulated, it 

 is evident from the foregoing, that the functional significance of 

 the adrenal system is enormous. 



It will be readily understood that the peculiar anatomical 

 arrangement of the adrenal system renders its total suppression, 

 w r hether experimentally or by pathological processes, impossible. 

 Once again it must be pointed out that extirpation of the supra- 

 renals is followed, not by suppression but, at the most, by in- 

 adequacy of the adrenal system, and that signs of a lowering of 

 the sympathetic nervous tone would hardly be the outcome of such 

 a condition. The most important of the symptoms of a lowered 

 vascular tone, namely, the fall in blood-pressure, is, as a matter 

 of fact, absent. It is true that accounts have been given of 

 changes in the metabolism of the carbohydrates. Moreover, the 

 symptomatology of Addison's disease does not permit the in- 

 ference that the condition is exclusively the outcome of the cessa- 

 tion of activity on the part of the adrenal system. For it is 

 highly probable that the symptom-complex of Addison's disease 

 includes the signs of disturbance of the suprarenal cortex, a dis- 

 turbance of which anatomical proof has frequently been forth- 

 coming. 



The effects which an abnormally increased adrenalina?mia has 

 upon the organism may be exactly estimated by means of experi- 

 ment. A condition of acute hyperadrenalinism is invariably 

 accompanied by symptoms of increased irritability on the part of 

 the sympathetic system. 



THE TNTERRENAL SYSTEM. 



The interrenal system is present in all vertebrates ; it takes 

 the form of paired or unpaired bodies of various sizes. It is 



