542 HANDBOOK OF PHYSIOLOGY. 



nerves, are mingled in its branches. The parts supplied by the branches 

 of the vagus nerve are as follows: 



(1.) By its pharyngeal branches, which enter the pharyngeal plexus, 

 a large portion of the mucous membrane, and, probably, all the muscles 

 of the pharynx. 



(2.) By the superior laryngeal nerve, the mucous membrane of the 

 under surface of the epiglottis, the glottis, and the greater part of the 

 larynx, and the crico-thyroid muscle. 



(3.) By the inferior laryngeal nerve, the mucous membrane and mus- 

 cular fibres of the trachea, the lower part of the pharynx and larynx, 

 and all the muscles of the larynx except the crico-thyroid. 



(4.) By its cesopJiageal branches, the mucous membrane and muscular 

 coats of the (Esophagus. 



(5.) Through the cardiac nerves, moreover, the branches of the vagus 

 form a large portion of the supply of nerves to the heart and the great 

 Arteries derived from both the trunk and the recurrent nerve. 



(6.) Through both the anterior and the posterior pulmonary plexuses 

 to the Lungs. 



(7.) Through its gastric branches and to the Stomach, by its termi- 

 nal branches passing over the walls of that organ. 



(8.) Through hepatic and splenic branches the Liver and the Spleen 

 are partly supplied with nerves. 



Communications. Throughout its whole course, the vagus contains 

 both sensory and motor fibres; but after it has emerged from the skull, 

 and, in some instances even sooner, it enters into so many anastomoses 

 that it is hard to say whether the filaments it contains are, from their 

 origin, its own, or whether they are derived from other nerves combining 

 with it. This is particularly the case with the filaments of the sym- 

 pathetic nerve, which are abundantly added to nearly all its branches. 

 The likeness to the sympathetic which it thus acquires is further in- 

 creased by its containing many filaments derived, not from the brain, 

 but from its own petrosal ganglia, in which filaments originate, in the 

 same manner as in the ganglia of the sympathetic, so abundantly that 

 the trunk of the nerve is visibly larger below the ganglia than above 

 them (Bidder and Volkmann). Next to the sympathetic nerve, that 

 which most communicates with the vagus is the accessory nerve, whose 

 internal branch joins its trunk, and is lost in it. 



Functions. The particular functions which the branches of the 

 pneumogastric nerve discharge in the several parts to which they are dis- 

 tributed, may be thus summarized. They show that 1. The pharyn- 

 geal branch is the principal motor nerve of the pharynx and soft palate, 

 and is most probably wholly motor; the chief part of its motor fibres 

 being derived from the internal branch of the accessory nerve. 2. The 

 inferior or recurrent laryngeal nerve is the motor nerve of the larynx. 



