THE INHIBITOR Y NER VES 7 3 



nerve ought to cause inhibition of the ileo-colic and pyloric 

 sphincters, but here our information is lacking. Elliott has not 

 been able to find any evidence of any action of the vagus nerve 

 on these muscles. There is this only to be said : if it is true, as 

 Dixon asserts, that in the case "of the stomach of the frog the 

 sympathetic system of muscles is the main system, so that stimu- 

 lation of the thoracic splanchnic causes contraction of the stomach, 

 then, seeing that he states at the same time that stimulation of 

 the vagus causes relaxation, there is evidence that the vagus 

 nerve does cause inhibition of the sympathetic musculature in 

 this region, just as it ought to do. 



With respect to the internal sphincter of the anus it does not 

 appear that all its motor cells are situated in the inferior mesen- 

 teric ganglion, for its contraction reflexly on stimulation of that 

 end of the cut hypogastric nerve which is connected with the 

 inferior mesenteric ganglion the so-called axon reflex implies 

 the existence of motor cells, either on the course of the hypo- 

 gastric nerve, or close to the muscle itself. It is suggestive, with 

 respect to the position of these cells, that Dale has found that 

 after the administration of ergotoxin, either stimulation of the 

 peripheral end of the hypogastric nerve or the application of 

 adrenalin causes a relaxation of the muscle, so that these outlying 

 sympathetic motor nerve cells are accompanied by outlying sym- 

 pathetic inhibitory nerve cells. From these two observations of 

 Elliott and Dale it would appear that the internal sphincter ani 

 muscle is composed of two parts, of which one is supplied by 

 motor and inhibitory neurons, which have travelled out together in 

 the thoracico-lumbar outflow and are situated near the muscle, and 

 the other is supplied by motor neurons belonging to the thoracico- 

 lumbar outflow and situated in the inferior mesenteric ganglion, 

 and by inhibitory neurons belonging to the sacral outflow. 



The exact point in the upper alimentary canal, where all influ- 

 ence of the sympathetic nerve ceases, is a doubtful point. All 

 observers agree that the splanchnic nerves do not affect the oeso- 

 phagus, either in the direction of contraction or inhibition. Both 

 motor and inhibitory nerves in this region belong to the vagus 

 outflow. Somewhere in the stomach is the termination of the 

 sympathetic nerve supply. Now Cannon has shown that the 

 cardiac end of the stomach is a receptacle for holding food, and 

 that the active churning movements are confined to the antrum 



