558 THE NERVOUS SYSTEM. 



through both the anterior and the posterior pulmonary 

 plexuses; and to the stomach, by its terminal branches 

 passing over the walls of that organ ; while branches are 

 also distributed to the liver and to the spleen. 



From the parts thus enumerated as receiving nerves from 

 the pneumogastric, it might be assumed that this latter is 

 a nerve of mixed function, both sensitive and motor. Expe- 

 riments prove that it is so from its origin, for the irritation 

 of its roots, even within the cranial cavity, produces both 

 pain and convulsive movements of the larynx and pharynx; 

 and when it is divided within the skull, the same move- 

 ments 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 combining 

 with it. This is particularly the case with the filaments I/ 

 of the sympathetic nerve, which are abundantly added to j[ 

 nearly all the branches of the pneumogastric. 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 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 



