CRANIAL NERVES. 101 



3. Inferior laryngeal, which sends its ultimate branches to all the in- 

 trinsic muscles ol the larynx except the crico-thyroid, and to the inferior 

 constrictor of the pharnyx. 



4. Cardiac branches given off from the nerve throughout its course, 

 which unite with the sympathetic fibres to form the cardiac plexus, to be 

 distributed to the heart. 



5. Pulmonary branches, which form a plexus of nerves and are dis- 

 tributed to the bronchi and their ultimate terminations, the lobules and air 

 cells. 



From the right pneumogastric 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 mem- 

 brane 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. 



