PNEUMOGASTRIC NERVE. 461 



muscles of the fauces and pharynx by reflex action. The food is 

 consequently grasped by these muscles, without the concurrence of 

 the will, and the process of deglutition is commenced. This action 

 is not only involuntary, but it will frequently take place even in 

 opposition to the will. The food, once past the isthmus of the fauces, 

 is beyond the control of volition, and cannot be returned except by 

 convulsive action, equally involuntary in its character. 



Natural stimulants, therefore, applied to the mucous membrane 

 of the pharynx, excite deglutition; unnatural stimulants, applied 

 to the same part, excite vomiting. If the finger be introduced into 

 the fauces and pharynx, or if the mucous membrane of these part? 

 be irritated by prolonged tickling with the end of a feather, the 

 sensation of nausea, conveyed through the glosso-pharyngeal nerve, 

 is sometimes so great as to produce immediate and copious vomit- 

 ing. This method may often be successfully employed in cases of 

 poisoning, when it is desirable to excite vomiting rapidly, and when 

 emetic medicines are not at hand. 



PXEUMOGASTRIC. Owing to the numerous connections of the 

 pneumogastric with other nerves, its varied and extensive distribu- 

 tion, and the important character of its functions, this is properly 

 regarded as one of the most remarkable nerves in the whole body. 

 Owing to the wandering course of its fibres, which are distributed 

 to no less than four different vital organs, viz., the heart, lungs, 

 stomach and liver, as well as to several other parts of secondary 

 importance, it has been often known by the name of the par vagum. 

 The pneumogastric arises, by a number of separate filaments, from 

 the lateral portion of the medulla oblongata, in the groove between 

 the olivary and restiform bodies. These filaments unite into a 

 single trunk, which emerges from the cranium by the jugular fora- 

 men, where it is provided with a longitudinal ganglionic swelling, 

 the " ganglion of the pneumogastric nerve." Immediately below 

 the level of this ganglion the nerve receives an important branch 

 of communication from the spinal accessory, and afterward from 

 the facial, the hypoglossal, and the anterior branches of the first 

 and second cervicals. 



At its origin, the pneumogastric is exclusively a sensitive nerve. 

 Irritated above the situation of its ganglion, it has been found to 

 convey painful sensations alone ; but if the irritation be applied at 

 a lower level, it causes at the same time muscular contractions, 

 owing to the filaments which it has received from the above-men- 



