THE PNEUMOGASTRIC NERVE. 439 



and convulsive movements of the larynx and pharynx ; and 

 when it is divided within the skull, the same movements follow 

 the irritation of the distal portion, showing that they are not 

 due to reflex action. Similar experiments prove that, through 

 its whole course, it contains both sensitive 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 com- 

 bining with it. This is particularly the case with the filaments 

 of the sympathetic nerve, which are abundantly added to 

 nearly all the branches of the pneumogastric. The likeness 

 to the sympathetic which it thus acquires is further increased 

 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 importantly commu- 

 nicates with the pneumogastric is the accessory nerve, whose 

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



Properly, therefore, the pneumogastric might be regarded 

 as a triple-mixed nerve, having out of its own sources, motor, 

 sensitive, and sympathetic or ganglionic nerve-fibres ; and to 

 this natural complexity it adds that which it derives from the 

 reception of filaments from the sympathetic, accessory, and 

 cervical nerves, and, probably, the glosso-pharyngeal and 

 facial. 



The most probable account of the particular functions which 

 the branches of the pneumogastric nerve discharge in the sev- 

 eral parts to which they are distributed, may be drawn from 

 Dr. John Reid's experiments on dogs. They show that: 1. 

 The pharyngeal branch is the principal, if not the sole motor 

 nerve of the pharynx and soft palate, and is most probably 

 wholly motor ; a part of its motor fibres being derived from 

 the internal branch of the accessory nerve. 2. The inferior 

 laryngeal nerve is the motor nerve of the larynx, irritation of 

 it producing vigorous movements of the arytenoid cartilages ; 

 while irritation of the superior laryngeal nerve gives rise to no 

 action in any of the muscles attached to the arytenoid carti- 

 lages, but merely to contractions of the crico-thyroid muscle. 

 3. The superior laryngeal nerve is chiefly sensitive; the in- 

 ferior, for the most part, motor ; for division of the recurrent 

 nerves puts an end to the motions of the glottis, but without 

 lessening the sensibility of the mucous membrane ; and division 

 of the superior laryngeal nerves leaves the movements of the 



