INTERNAL SECRETION 503 



.are in other regions of the body. Applied locally to the mucous membranes, 



[adrenalin extract produces contraction of the blood-vessels as shown by the 



[pallor which follows. 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. 



In the foregoing instances the extract apparently produces its effects by 



an augmentation of the normal tonus of the arteriole muscle. The effects 



follow the injection of an extract of the medulla only. An extract of the 



cortex appears to be without influence. 



The injection of small doses of the active principle of the gland into the 

 peritoneal 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 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 secretion 

 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 augments 

 the tone and the vigor of the spontaneous contractions. In addition to the 

 foregoing phenomena, dilatation of the pupil, increased flow of saliva and 

 glycosuria have been observed. 



From an examination of the effects that follow the intravenous injection 

 of adrenalin or adrenal extracts, it is apparent that they closely resemble the 

 effects that follow stimulation of the sympathetic nerve in a large part if not 

 in all parts, of its distribution. 



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 

 muscles that have been deprived of their nerve connections through degenera- 

 tive changes following division of the nerves, are influenced by adrenalin, 

 have led to the assumption that it acts neither on muscle nor nerve, but on 

 some material which intervenes between the nerve endings and the muscle 



