112 HUMAN PHYSIOLOGY. 



From the right pneumogastrlc nerve branches are distributed to the 

 mucous membrane and muscular coats of the stomach and intestines, to the 

 liver, spleen, kidneys, and supra-renal capsules. 



Properties. At its origin the pneumogastric nerve is sensory, as shown 

 by direct irritation or galvanization, though its sensibility is not very 

 marked. In its course exhibits motor properties, from anastomosis with 

 motor nerves. 



The Pharyngeal branches assist in giving sensibility to the mucous 

 membrane of the pharynx, and influence reflex phenomena of deglutition 

 through motor fibres which they contain, derived from the spinal 

 accessory. 



The Superior laryngeal nerve endows the upper portion of the larynx 

 with sensibility ; protects it from the entrance of foreign bodies ; by con- 

 ducting impressions to the medulla, excites the reflex movements of deglu- 

 tition and respiration; through the motor filaments it contains produces 

 contraction of the crico-thyroid muscle. 



Division of the " Depressor nerve" and galvanization of the central 

 end, retards and even arrests the pulsations of the heart, and by depressing 

 the vasomotor centre diminishes 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 fibres from 

 the spinal accessory. When irritated produces movement in the laryn- 

 geal muscles. When divided, is followed by paralysis of these muscles, 

 except the crico-thyroid, impairment of phonation, and an embarrassment 

 of the respiratory movements of the larynx, and finally death, from suffo- 

 cation. 



The Cardiac branches, through filaments derived from the spinal acces- 

 sory, exert a direct inhibitory action upon the heart. Division of the 

 pneumogastrics in the neck increases the frequency of the heart's action. 

 Galvanization of the peripheral ends diminishes the heart's pulsation, and, 

 if sufficiently powerful, paralyzes 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, falling as low as four to six per minute ; death usually occurs 

 in from five to eight days. Feeble galvanization of the central ends of the 

 divided nerves accelerates respiration ; powerful galvanization retards, and 

 may even arrest the respiratory movements. 



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



