THE PNEUMOGASTRIC NERVE. 559 



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 Yolkmann). Next to the sympathetic nerve, 

 that which most importantly communicates with the pneu- 

 mogastric is the accessory nerve, whose internal branch 

 joins its trunk, and is lost in it. 



Properly, therefore, the pneumogastric might be re- 

 garded 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 several parts to which they are distributed, may be 

 drawn from Dr. John Reid's experiments on dogs. They 

 show that, i. 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 acces- 

 sory 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 cartilages, but 

 merely to contractions of the crico-thyroid muscle. 3. The 

 superior laryngeal nerve is chiefly sensitive ; the inferior, 

 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 



