INTERNAL SECRETION 507 



muscles in these organs are not so abundantly supplied with vaso-motor 

 nerves as they are in other regions of the body. Applied locally to the 

 mucous membranes, adrenal extract produces contraction of the blood- 

 vessels as shown by the pallor which follows. In the foregoing instances 

 the extract apparently produces its effects by an augmentation of the 

 normal tonus of the arteriole muscle. The skeletal muscles are affected 

 by the extract very much as they are by veratrin. The duration of a 

 single contraction is very much prolonged, especially in the phase of 

 relaxation or of decreasing energy. These effects follow the injection 

 of an extract of the medulla only. An extract of the cortex appears to 

 be without influence. 



The action of adrenal extract however is not limited to the non-striated 

 muscle-fibers of the arterioles but extends itself to the non-striated fibers 

 found in the the walls of the viscera, e.g., stomach and intestines, gall- 

 bladder, urinary bladder, uterus, etc. The administration of this extract 

 is followed however, in these regions, by an inhibition of the tonus and 

 subsequent relaxation of the visceral walls, with the exception of the uterus. 

 In the case of the isolated virgin uterus of many mammals, adrenal extract 

 augments the tone and the vigor of the spontaneous contractions. In addi- 

 tion to the foregoing phenomena, dilatation of the pupil, and increased flow 

 of saliva have been observed. 



The injection of small doses of the extract of the gland into the perito- 

 neal cavity or into the blood is also followed by glycosuria in the course 

 of an hour which may last for several hours. 



The Internal Secretion. It is apparent from the results of these experi- 

 ments that the adrenal bodies are engaged in elaborating and pouring into 

 the blood a specific material which on the one hand stimulates to increased 

 activity the muscle-fibers of the heart and arteries, thus assisting in main- 

 taining the normal blood-pressure, and on the other hand maintaining the 

 tonicity of the skeletal muscles. An alkaloidal substance was isolated by 

 Abel from extracts of this gland, to which the term epinephrin was given. A 

 crystallizable substance was isolated first by Takamine and later by Aldrich, 

 to which the term adrenalin was given. Both substances are apparently 

 equally efficacious in causing contraction of the blood-vessels and in raising 

 the blood-pressure. Epinephrin or adrenalin represents the active principle 

 of the gland and is regarded as a product of the secretor activity of the 

 cells composing the medulla. As the effects following the intravenous injec- 

 tion of adrenalin are of short duration, the supposition is that it is speedily 

 oxidized. It is regarded as the typical hormone. 



The Seat of Action of Adrenalin. The effects which follow the intra- 

 venous injection of adrenalin or adrenal extracts resemble in many respects 

 the effects which follow stimulation of the sympathetic nerves, i.e., vaso- 

 motor and viscero-motor nerves in a large part, if not all parts, of their 

 distribution, and therefore lead to the inference that adrenalin supple- 

 ments or augments the action of the sympathetic nerves. 



It has been a subject of discussion as to whether adrenalin acts on the 

 muscle-fiber directly or upon the endings of the sympathetic nerves with which 

 they are functionally associated. By reason of the fact that non-striated 

 muscles that have no connections with the sympathetic nerve system, are 

 not influenced by adrenalin; and the further fact that non-striated 



