206 HUMAN PHYSIOLOGY. 



The superior laryngeal nerve endows the upper portion of the larynx with 

 sensibility; protects it from the entrance of foreign bodies; by conducting 

 impressions to the medulla, excites the reflex movements of deglutition and 

 respiration; through the motor filaments it contains, produces contraction of 

 the cricothyroid muscle. 



Division of the "depressor nerve" and galvanization of the central end 

 retard and even arrest the pulsations of the heart, and by depressing the vaso- 

 motor center, diminish the pressure of blood in the large vessels, by causing 

 dilatation of the intestinal vessels through the splanchnic nerves. 



The inferior laryngeal contains, for the most part, motor fibers from the 

 spinal accessory. When irritated, produces movement in the laryngeal mus- 

 cles. When divided, is followed by paralysis of these muscles, except the 

 cricothyroid, impairment of phonation, and an embarrassment of the 

 respiratory movements of the larynx, and, finally, death from suffocation. 



The cardiac branches, through filaments derived from the spinal accessory, 

 or possibly from the medulla oblongata direct, exert a direct inhibitory action 

 upon the heart. Division of the pneumogastrics in the neck' is followed 

 by increased frequency of the heart's action. Galvanization of the peripheral 

 ends diminishes the heart's pulsations, and, if sufficiently powerful, arrests 

 it in diastole. 



The pulmonary branches give sensibility to the bronchial mucous membrane 

 and govern the movements of respiration. Division of both pneumogastrics 

 in the neck diminishes the frequency of the respiratory movements, which 

 may fall as low as four to six a minute; death usually occurs in from five to 

 eight days. Feeble galvanization of the central ends of the divided nerves 

 acclerates respiration; powerful galvanization retards, and may even arrest 

 the respiratory movements. 



The gastric branches give sensibility to the mucous coat, and through 

 motor or efferent fibers give motion to the muscular coat of the stomach. 

 They influence the secretion of gastric juice, and aid the process of digestion. 



The hepatic branches, probably through anastomosing sympathetic fila- 

 ments, influence the secretion of bile and the glycogenic function of the liver; 

 division of the pneumogastrics in the neck produces congestion of the liver, 

 diminishes the density of the bile, and arrests the glycogenic function; gal- 

 vanization of the central ends exaggerates the glycogenic function and makes 

 the animal diabetic. 



The intestinal branches give sensibility and motion to the small intestines. 



Function. A great sensor nerve, which, through filaments from motor 

 sources, influences deglutition, the action of the heart, the circulatory and 

 respiratory systems, voice, the secretions of the stomach, intestines, and vari- 



