560 THE NERVOUS SYSTEM. 



movements of the glottis unaffected, but deprives it of its 

 sensibility. 4. The motions of the oesophagus are depen- 

 dent on motor fibres of the pneumogastric, and are pro- 

 bably excited by impressions made upon sensitive fibres of 

 the same ; for irritation of its trunk excites motions of the 

 oesophagus, which extend over the cardiac portion of the 

 stomach ; and division of the trunk paralyzes the oeso- 

 phagus, which then becomes distended with the food. 

 5. The cardiac branches of the pneumogastric nerve are 

 one, but not the sole channel through which the influence 

 of the central organs and of mental emotions is transmitted 

 to the heart. 6. The pulmonary branches form the prin- 

 cipal, but not the sole channel by which the impressions 

 on the mucous surface of the lungs that excite respiration, 

 are transmitted to the medulla oblongata. Dr. Reid was 

 unable to determine whether they contain motor fibres. 



From these results, and by referring to what has been 

 said in former chapters, the share which the pneumogastric 

 nerve takes in the functions of the several parts to which 

 it sends branches, may be understood : 



1 . In deglutition, the motions of the pharynx are of the 

 reflex kind. The stimulus of the food, or other substance 

 to be swallowed, acting on the filaments of the glosso- 

 pharyngeal nerve as well as the filaments of the superior 

 laryngeal given to the pharynx, and of some other nerves, 

 perhaps, with which these communicate, is conducted to the 

 medulla oblongata, whence it is reflected, chiefly through 

 the pneumogastric, to the muscles of the pharynx. 



2. In the functions of the larynx, the sensitive filaments 

 of the pneumogastric supply that acute sensibility by 

 which the glottis is guarded against the ingress of foreign 

 bodies, or of irrespirable gases. The contact of these 

 stimulates the filaments of the superior laryngeal branch 

 of the pneumogastric ; and the impression conveyed to the 

 medulla oblongata, whether it produce sensation or not, 

 is reflected to the filaments of the recurrent or inferior 



