648 NERVOUS SYSTEM. 



The important physiological point connected with the anatomy of the recurrent laryn- 

 geals is that they animate all of the intrinsic muscles of the larynx, except the crico-thy- 

 roid. Experiments have shown that these nerves contain numerous filaments from the 

 spinal accessory. 



The cervical cardiac branches, two or three in number, arise from the pneumogastrics 

 at different points in the cervical portion and pass to the cardiac plexus, which is formed 

 in great part of filaments from the sympathetic. The thoracic cardiac branches are 

 given off from the pneumogastrics below the origin of the inferior laryngeals and join 

 the cardiac plexus. 



The anterior pulmonary branches are few and delicate as compared with the posterior 

 branches. They are given oft' below the origin of the thoracic cardiac branches, send a 

 few filaments to the trachea, and then form a plexus which surrounds the bronchial tubes 

 and follows the bronchial tree to its terminations in the air-cells. The posterior pulmonary 

 branches are larger and more numerous than the anterior. They communicate freely 

 with sympathetic filaments from the upper three or four thoracic ganglia and then form 

 the great posterior pulmonary plexus. From this plexus, a few filaments go to the infe- 

 rior and posterior portion of the trachea, a few pass to the muscular tissue and mucous 

 membrane of the middle portion of the oesophagus, and a few are sent to the posterior 

 and superior portion of the pericardium. The plexus then surrounds the bronchial tree 

 and passes with its ramifications to the pulmonary tissue, like the corresponding fila- 

 ments of the anterior branches. The pulmonary branches are distributed to the mucous 

 membrane, and not to the walls of the blood-vessels. 



The oesophageal branches take their origin from the pneumogastrics above and below 

 the pulmonary branches. These branches from the two sides join to form the cesopha- 

 geal plexus, their filaments of distribution going to the muscular tissue and the mucous 

 membrane of the lower third of the oesophagus. 



The abdominal branches are quite different in their distribution upon the two sides. 



Upon the left side, the nerve, which is situated anterior to the cardiac opening of the 

 stomach, immediately after its passage by the side of the oesophagus into the abdomen, 

 divides into numerous branches, which are distributed to the muscular walls and the 

 mucous membrane of the stomach. As the branches pass from the lesser curvature, they 

 take a downward direction and go to the liver, and, with another branch running between 

 the folds of the gastro-hepatic omentum, they follow the course of the portal vein in the- 

 hepatic substance. The branches of this nerve anastomose with the nerve of the right 

 side and with the sympathetic. 



The right pneumogastric, situated posteriorly, at the cesophageal opening of the dia- 

 phragm, sends a few filaments to the muscular coat and the mucous membrane of the 

 stomach, passes backward, and is distributed to the liver, spleen, kidneys, suprarenal 

 capsules, and finally to the whole of the small intestine. The branches to the small intes- 

 tine are very important. These were accurately described in 1860, by Kollmann, in an 

 elaborate and beautifully-illustrated prize-essay. In the plate showing the distribution 

 of this nerve, it is seen that the branches to the intestine are very numerous. Accord- 

 ing to these researches, the branches described belong to the pneumogastric itself and 

 are not derived from the sympathetic. When we come to treat of the action of the pneu- 

 mogastric upon the small intestine, it will be seen that the anatomical researches by Koll- 

 mann have been fully confirmed by physiological experiments. Before the nerves pass 

 to the intestines, there is a free anastomosis and interchange of filaments between the 

 right and the left pneumogastric. 



Properties and Functions of the Pneumogastric Nerves. 

 There is no^nerve in the body that has been the subject of so many experiments, and 

 concerning which so much has been written, as the pneumogastric. Its accessible posi- 

 tion in many parts of its course, its extensive connections with the digestive, the respira- 



