840 TEE NERVES. 



cules of the bronchial plexus, each pneumogastric is continued along the 

 oesophagus by two branches — a superior and inferior — making four branches 

 for the two nerves. The two superior lie together, and form a single cord, 

 either immediately or after a certain course : the two inferior comport them- 

 selves in the same manner with one another — making a double anastomosis, from 

 which arise the two nerves we are about to describe, and which are designated 

 the oesophageal nerves, because of their situation. The right nerve forms a large 

 portion of the superior cord ; the left, especially, gives ramuscules to the inferior. 



Placed between the layers of the posterior mediastinum, these two nerves 

 follow the oesophagus for a certain distance — one above, the other below — giving 

 off some ramuscules to that muscular tube, detaching one or two communicating 

 branches, and traversing the foramen sinistrum in the diaphragm to enter the 

 abdominal cavity. 



The inferior terminates in the parieties of the stomach, by forming on the 

 small curvature, to the right of the cardia, a very rich pre-stomachal plexus, 

 which throws the majority of its ramuscules on the right sac of that viscus. 



The superior passes to the left of the oesophageal insertion, along with the 

 gastro-pulmonary artery, and is lost in the solar plexus, after giving off numerous 

 divisions on the left sac of the stomach, mixing with the sympathetic ramuscules 

 that encircle the gastric artery, and anastomosing around the cardia with those 

 of the inferior cord. It is very difficult to follow the filaments of this cord from 

 the pneumogastrics after their arrival at the solar plexus ; we nevertheless observe 

 some of them passing to the liver, others accompanying the sympathetic branches 

 that come from the solar to the posterior mesenteric plexus in following the 

 small mesenteric vein ; and no doubt others find their way among the filaments 

 of the trisplanchnic nerve, which proceed with the anterior mesenteric artery. 



Functions of the Pneumogastric. — Formed by the two orders of fibres, 

 the pneumogastric is a sensory-motor nerve, and the seat ot reflex currents which 

 make it play a very important part in several acts of vegetative life, and bring it 

 into relationship with the great sympathetic nerve, with which we have seen that 

 the tenth pair maintains anastomotic connections in several points of its course. 



It is the pneumogastric nerve that gives to the mucous membrane of the 

 larynx the exquisite sensibility it enjoys. 



It stimulates the motor muscles of the larynx to movement. 



To it is also due the sensibility of the broncho-pulmonary mucous membrane. 



It causes contractions of the muscular fibres in the broncho-tracheal passages 

 — contractions which are involuntary, and due to reflex influence. 



It also causes movements of the oesophagus and the stomach, which are 

 involuntary and due to reflex currents. 



Perhaps it acts in an analogous manner — by reflex action — in the secretion of 

 the gastric fluid and the functions of the Hver ; but these are points which science 

 has not yet determined. 



It appears proved that it exercises an influence on the essential phenomena of 

 respiration (liaulanie), as it participates in the centripetal stimulation which 

 brings the respiratory mechanism into play. 



It transmits to the heart the influence of the moderating centre of that organ 

 which is situated at its roots in the meduUa oblongata. 



After its section in the region of the neck, the movements of the heart 

 become very precipitate, and we may diminish the force of these movements, or 

 even completely arrest them, by galvanizing the peripheral end of the nerve. In 



