THE SUPRARENAL SYSTEM 227 



peripheral terminals of those nerves, the central stimulation of 

 which produces the effect of " heat-puncture." 



The tables on pp. 222 to 225 show the effects of adrenalin in so 

 far as they are at present known. For purposes of comparison, 

 they also include all that is at present known concerning the 

 sympathetic and autonomous innervation of the vegetative organs. 



THE SITE OF ACTION OF ADRENALIN. 



In his first work upon the effects of suprarenal extract (1901), 

 Langley emphasized the fact that the results produced by this 

 substance are never identical with those obtained by stimulation 

 of the cranial-autonomous or sacral-autonomous nerves. Phen- 

 omena exactly similar to those obtained in the eye, by stimulation 

 of the oculomotor ; in the heart and intestinal canal by stimulation 

 of the vagus ; in the rectum, urinary bladder, and internal genitals 

 by stimulation of the pelvic nerve, are never produced by supra- 

 renal extract. The increased secretion of saliva cannot be 

 regarded as an exception to this rule, for it is not accompanied 

 by vaso-dilation such as that which accompanies stimulation of 

 the chorda tympani. On the other hand, it is noticeable that the 

 effects which suprarenal extract produces are, in nearly all cases, 

 similar to those obtained by stimulation of the sympathetic 

 autonomous nerves. In many instances, the effect of the extract 

 and that of electric stimulus of the sympathetic are identical. These 

 results seem to point directly to the view that suprarenal extract 

 exercises a specific stimulatory action upon the sympathetic nerve- 

 terminals. Yet, in view of the fact that, in the case of the eye, 

 the vessels, the submaxillary gland, and the muscles of the hair, 

 this action is constant after degeneration of the post-ganglionary 

 fibres, Langley was compelled to admit that suprarenal extract 

 may also have a direct influence upon the unstriated muscles. 



Four years later, Elliott drew attention to the fact that, in 

 spite of the difference in the method of the sympathetic innervation 

 in different animal species, the effects of adrenalin upon the 

 involuntary muscles were everywhere the same as those produced 

 by stimulation of the nerves supplying them. The strength of the 

 effect varies only with the frequency of the normal physiological 

 impulse, which individual muscles receive during life by the 

 agency of the sympathetic. The physiological stimulatory action of 

 adrenalin is undoubtedly peripheral, but the question as to which 

 portion of the periphery is the site of its activity demands further 

 investigation. This site is most probably to be sought, either in 

 the peripheral sympathetic nerve-terminals, or in the unstriated 

 muscles themselves. 



That adrenalin exercises a direct action upon the muscles, was 

 suggested by various phenomena and was, until recently, assumed 

 by the greater number of authors. Lewandowsky and even 



