PNEUMOGASTRIC NERVE. 583 



upon respiration. TJie pulmonary branches themselves are so deeply situated 

 that they have not as yet been made the subject of direct experiment, with 

 any positive and satisfactory results. 



Properties and Uses of the (Esopliageal Nerves. The muscular walls and 

 the mucous membrane of the oesophagus are supplied entirely by branches 

 from the pneumogastrics. The upper portion is supplied by filaments from 

 the inferior laryngeal branches, the middle portion, by filaments from the 

 posterior pulmonary branches, and the inferior portion receives the cesopha- 

 geal branches. These branches are both sensory and motor ; but probably 

 the motor filaments largely predominate, for the mucous membrane, although 

 it is sensible to the extremes of heat and cold, the feeling of distention, and 

 a burning sensation upon the application of strong irritants, is by no means 

 acutely sensitive. 



That the movements of the oesophagus are animated by branches from 

 the pneumogastrics, has been clearly shown by experiments. In the first 

 place, except in animals in which the anatomical distribution of the nerves 

 is different from the arrangement in the human subject, the entire oesopha- 

 gus is paralyzed by dividing the nerves in the neck. When the pneumogas- 

 trics are divided in the cervical region in dogs, if the animals attempt to 

 swallow a considerable quantity of food, the upper part of the O3sophagus is 

 found enormously distended. Bernard noted in a dog in which a gastric 

 fistula had been established, that articles of food given to the animal did not 

 pass into the stomach, although he made great efforts to swallow. An in- 

 stant after the attempt, the matters were regurgitated, mixed with mucus, 

 but of course did not come from the stomach. 



Direct experiments upon the roots of the pneumogastrics have shown that 

 these nerves influence the movements of the oesophagus, and that the motor 

 filaments involved do not come from the spinal accessory ; but it is not known 

 from what nerves these motor filaments are derived. 



Properties and Uses of the Abdominal Nerves. In view of the exten- 

 sive distribution of the terminal branches of the pneumogastrics to the ab- 

 dominal organs, it is evident that the action of these nerves must be very 

 important, particularly since it has been shown that the right nerve is dis- 

 tributed to the whole of the small intestine. 



Influence of the Pneumogastrics upon the Liver. There is very little 

 known with regard to the influence of the pneumogastrics upon the se- 

 cretion of bile ; and the most important experiments upon the innervafion 

 of the liver relate to the production of glycogen. If both pneumogastrics be 

 divided in the neck, and if the animal be killed at a time varying between a 

 few hours and one or two days after, the liver contains no sugar, under the 

 conditions in which it is generally found ; viz., a certain time after death. 

 From experiments of this kind, Bernard concluded that the glycogenic pro- 

 cesses are suspended when the nerves are divided. The experiments, how- 

 ever, made by irritating the pneumogastrics, were more satisfactory, as in 

 these he looked for sugar in the blood and in the urine and did not confine 

 his examinations for sugar to the substance of the liver. 



