THE DUCTLESS GLANDS 1185 



and katabolic, that only the latter are stimulated by central irritation, 

 whereas electrical stimulation, exciting both sets of fibres, causes an increased 

 production of adrenaline in the gland, which exactly keeps pace with the 

 increased output. 



When adrenaline is injected into the blood-stream the effect is only 

 temporary. It is not excreted in the urine, but rapidly disappears from the 

 blood. Since it is easily oxidised and is extremely unstable in alkaline 

 solution, we may conclude that after performing its excitatory function it is 

 destroyed by oxidation in- the fluids. Adrenaline is thus a typical hormone, 

 a body of comparatively low molecular weight, having a drug- like excitatory 

 action on specific tissues of the body, easily diffusible, and rapidly destroyed 

 after discharging its office. 



Owing to the rapid destruction of adrenaline, relatively enormous doses have to be 

 given by the mouth in order to produce any effect on the blood-pressure. There is, 

 however, a whole series of substances, more or less allied to adrenaline in chemical con* 

 stitution, which undergo less rapid destruction and can therefore be administered 

 as drugs in the usual way. Dale and Barger have recently described three such sub- 

 stances as occurring in infusions of putrid meat and as forming the most important of 

 the active principles of ergot. The constitution of these substances is shown in the 

 following formulae : 



3 \CHCH 2 CH 2 NH 2 Isoamylamine 



CH 2 CH 2 NH 2 p-hydroxyphenylethylamine 



CH 2 CH 2 NH 2 phenylethylamine 



CH(OH)CH 2 NHCH 3 adrenaline 



The formula of adrenaline is placed below in order to show the relation of these 

 substances to the natural hormone. These bodies are produced from the amino -acids 

 of proteins by a process of decarboxylation. Leucine would yield isoamylamine, 

 tyrosine, hydroxyphenylethylamine, and phenylalanine would give phenylethylamine. 

 Such substances may be formed in minute quantities during the normal processes of 

 putrefaction which occur in the alimentary canal. 



There seems little doubt that we must regard adrenaline as a true internal 

 secretion, and therefore must ascribe to the medulla of the suprarenal capsules 

 as well as to the other chromaffine tissue in the body, the function of main- 

 taining the normal constriction of the arterioles and of facilitating in some 

 way or other the functions of the sympathetic system generally. The 

 absence of this secretion in cases of destruction by disease of the suprarenal s 

 would serve to account for the weakness, prostration, and lowered blood- 

 pressure of Addison's disease. The two other symptoms of this disease, 

 namely, bronzing and vomiting, still remain to be accounted for. It is 

 possible that the latter may be due to some involvement by the morbid 

 process of the numberless fibres of the solar plexus, which run in close 

 proximity to the suprarenals. We have no knowledge whatsoever of the 

 functions of the cortical portion of these organs. It is possible that future 



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