528 PHYSIOLOGY 



run with the branches of the fifth nerve, to supply secretory fibres 

 and possibly vaso- dilator fibres to the mucous membrane of the nose, 

 soft palate, and upper part of the pharynx. The glossopharyngeal 

 or ninth nerve sends fibres, which evoke secretion as well as vaso- 

 dilatation in the parotid gland, via the otic ganglion. Probably also 

 dilator fibres leave this nerve to supply vessels at the back of the 

 tongue. 



THE VAGUS 



The efferent visceral fibres of the tenth and eleventh nerves arise 

 in the same column of cells as the two nerves just considered. Most 

 of the fibres run in the vagus. They include motor fibres to the 

 oesophagus, stomach, and small intestines as far as the ileocolic 

 sphincter ; inhibitory fibres to the heart, motor fibres to the un- 

 striated muscles of the bronchi, and secretory fibres to the gastric 

 glands. The cell stations of these fibres are apparently situated 

 peripherally, the jugular ganglion, and the ganglion of the trunk 

 of the vagus being in all likelihood responsible only foi the afferent 

 fibres in this nerve. Nicotine therefore abolishes any effect of stimu- 

 lating the vagus in the neck, though inhibition of the heart can still 

 be produced on excitation of the post-ganglionic fibres arising from 

 the cells in the sinus venosus. 



SACRAL AUTONOMIC FIBRES 



These all run in the pelvic visceral nerve, also called nervus 

 erigens. This nerve is connected with a collection of ganglia lying 

 in the hypogastric plexus at the base of the bladder. It has the 

 following functions : 



Dilator to vessels of the penis (hence its name of nervus erigens). 



Motor to bladder, colon, and rectum. 



Inhibitory to sphincter muscle of bladder. 



Inhibitory to retractor penis. 



It will be observed that in many cases the viscera get their nerve 

 supply from both sets of visceral nerves, and that in such cases the 

 two sets of nerves are antagonistic in function. It is impossible, 

 however, to draw a sharp line between the functions of the two sets, 

 since the same nerve may be motor for one set of muscular fibres 

 and inhibitory for another set in the same viscus. Thus the colonic 

 branches of the inferior mesenteric ganglion are motor (constrictor) 

 for the blood-vessels and inhibitory for the muscular walls of the 

 colon. While the sympathetic nerve-supply is inhibitory for nearly the 

 whole intestinal muscles, it produces strong contraction of the band 

 of muscle forming the ileocolic sphincter. In the bladder there is 

 no doubt that the sympathetic supply includes both inhibitory and 



