542 NERVOUS SYSTEM 



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

 filaments from the posterior pulmonary branches, and the inferior por- 

 tion receives the cesophageal branches. These branches are both sen- 

 sory 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 on the 

 application of strong irritants, is not 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 oesophagus is paralyzed by division of the nerves in the neck. 

 When the pneumogastrics are divided in the cervical region in dogs, if 

 the animals attempt to swallow a considerable quantity of food, the 

 upper part of the oesophagus is found enormously distended. Bernard 

 noted in a dog in which a gastric fistula had been established, that arti- 

 cles of food given to the animal did not pass into the stomach, although 

 he made efforts to swallow. An instant after the attempt, the matters 

 were regurgitated, mixed with mucus, but of course did not come from 

 the stomach. 



Direct experiments on 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 accessories ; 

 but it is not known from what nerves these motor filaments are derived. 



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

 extensive distribution of the terminal branches of the pneumogastrics 

 to the abdominal organs, it is evident that the action of these nerves 

 must be important, particularly since it has been shown that the right 

 nerve is distributed to the entire small intestine. 



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

 known in regard to the influence of the pneumogastrics on the secretion 

 of bile ; and the most important experiments on the innervation of the 

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

 divided in the neck, and if the animal is 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 usually is found. From experiments 

 of this kind, Bernard concluded that the glycogenic processes are sus- 

 pended when the nerves are divided. The experiments, however, 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. 



After division of pneumogastrics in the neck, if the peripheral ends 



