4 66 TEXT-BOOK OF PHYSIOLOGY. 



extracts of this gland, to which the term epinephrin was given. A crystalli- 

 zable 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. The question as to which of these two substances represents the 

 active principle of the gland is as yet a subject of discussion. 



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 contraction and 

 a subsequent relaxation of the visceral walls. In these instances the extract 

 or the active principle produces its effects apparently by an inhibition of 

 the tonus of the visceral muscle. 



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 nerve connections with the sympathetic 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 

 but which is intimately related to the muscle. To this material Langley 

 has applied the term "receptive substance." 



Influence of the Nerve System. The secretory activity of the adrenals 

 is regulated by the nerve system. Thus Dreyer found that the blood of the 

 adrenal vein after stimulation of the splanchnics was capable of causing to a 

 much greater extent the usual physiologic effects when injected into an 

 animal than blood of the adrenal vein before stimulation and this indepen- 

 dent of the vascular changes that were simultaneously provoked. It has also 

 been shown by Ascher that a high blood-pressure can be maintained by 

 prolonged stimulation of the splanchnics. Cannon has reported that major 

 emotional disturbances such as fright lead to an increase in the secretion 

 of the adrenals as shown by the fact that the blood taken from the vena cava 

 above the level of the adrenal veins will promptly produce an inhibition 

 of a contracting intestinal strip, while blood taken from the animal previous 

 to the fright, had no such effect. After ligation of the veins and removal 

 of the adrenals there was a failure of this effect upon excitement. 



Emotional excitement in cats at least is also attended with hypergly- 

 cemia and glycosuria which is probably due to an increase of the adrenal 

 secretion in the blood inasmuch as a similar effect follows the injection of the 

 extract into the blood. The hyperglycemia and glycosuria caused either 

 by the intraveneous injection of the extract or by an increased activity of the 

 adrenals following emotional excitement, fear or rage, is difficult of explana- 

 tion. It may be the result of a direct action or an indirect action through 

 secretor nerves on the liver cells, in consequence of which the stored glycogen 

 is rapidly transformed into sugar and discharged into the blood. 



An advantage that would accrue to the animal from the accumulation 



