THE SUPRARENAL SYSTEM 197 



found that the effect of suprarenal extract is much stronger be- 

 fore than after the exhibition of curarin, and it seems certain from 

 this that the peripheral nervous elements play the chief part in 

 the production of vaso-constriction. 



Langley found that, in the case of the submaxillary gland, 

 even where the post-ganglionary fibres had undergone degenera- 

 tion, the intravenous injection of suprarenal extract was followed 

 by constriction only of the vessels, and he believed that the action 

 of the substance was, in all probability, directly muscular. He 

 emphasizes the fact, however, that the effects of suprarenal extract 

 vary in different parts of the vascular system, and he draws atten- 

 tion to the parallel between the action of this substance and the 

 effects of electric stimulus upon the sympathetic nerves. 



According to Brodie and Dixon, the fact that the influence of 

 adrenalin upon the pulmonary vessels is negative, is a sufficient 

 proof that this substance affects the sympathetic nerve endings 

 and these only, and has no influence whatever upon the unstriated 

 muscles. 



In order to test the effects of adrenalin upon the nerve ter- 

 minals, these authors first induced, by means of cocaine, curarin, 

 or apocodein, a paralysis of the systemic vaso-constrictor nerve 

 fibres. They were unable to obtain satisfactory results with 

 cocaine, but they found that, after curarin, the action of adrenalin, 

 although not entirely neutralized, was very much slighter in effect. 

 Lawen, on the other hand, found that the effects of suprarenin, 

 when introduced into the circulation of frogs previously treated 

 with curarin, were in no way diminished; he concludes from this 

 that there is not a direct antagonism between curarin and supra- 

 renin, and he believes that suprarenin exercises a direct action 

 upon the muscular structure of the vessels. 



Dixon 's experiments with apocodein bring an even more 

 certain proof of the effects of adrenalin upon the nerve terminals 

 of the vessels of both the heart and the intestine. Dixon showed 

 that apocodein, which is an alkaloid obtained by dehydration from 

 codein, when given in moderate doses, affects the sympathetic 

 nerve cells in exactly the same way as nicotine. A moderate dose 

 of apocodein causes vaso-dilation with consequent hypotension ; 

 it accelerates the heart's action ; and it intensifies the autonomous 

 movements of the unstriated muscles of the intestine. Apocodein 

 in moderate doses does not in any way affect the physiological 

 action of adrenalin. 



When given in large doses, apocodein produces a paralysis 

 of the nerve terminals of the striated muscles, similar to that 

 caused by curarin ; a paralysis of the vagus terminals in the 

 heart, similar to that produced by atropine ; and a complete para- 

 lysis of the vaso-motor nerve endings. At this stage of apocodein 

 poisoning, adrenalin does not provoke a rise in blood-pressure 

 nor does it affect the portions of the intestine which have a sym- 



