736 THE NERVES. 



which throws the majority of its ramuscules into 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 mesaraic 

 vein ; no doubt the 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 of reflux 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 connexions 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 that organ into movement. 



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

 membrane. 



It excites the contractions of the muscular fibres in the broncho- tracheal 

 passages contractions which are involuntary, and under the influence of the 

 reflex power. 



It also provokes the movements of the oesophagus and stomach, 'which 

 are also 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 liver ; but these are 

 points which science has not yet decided upon. 



It appears proved that it does not exercise any direct influence on the 

 essential phenomena of respiration. 



It also appears proved that it acts on the heart in a very energetic 

 manner, though this has been imperfectly determined. We only know that 

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

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

 movements, or even completely arrest them, by galvanising the peripheral 

 end of the nerve. 



11. Eleventh Pair, Spinal Nerves, or Accessory Nerves of the Pneumogastrics. 



(Fig. 338, 2, 4) 



The spinal accessory is an exclusively motor nerve, which, at its exit 

 from the cranium, is so intimately connected with the pneumogastric, that 

 we might perhaps follow the example of Miiller, and describe the two as 

 forming one and the same pair. 



Origin. This nerve exhibits a singular disposition, in that it arises from 

 the whole extent of the cervical spinal cord, and ascends in the spinal canal 

 to near the pneumogastric, with which it leaves the cranium by the pos- 

 terior foramen lacerum. It is also described as an encephalic nerve, in 

 conseqnonce of the latter peculiarity ; but from its origin it is rather a 



