THE CRANIAL NERVES. 229 



found in the rabbit, is formed by the union of two branches, one 

 from the superior laryngeal, the other from the main trunk ; it 

 passes downward to be distributed to the heart. 



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

 intrinsic muscles of the larynx except the cricothyroid, and to 

 the inferior constrictor of the pharynx. 



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

 which unite with the sympathetic fibers 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 intes- 

 tines, and to the liver, spleen, kidneys, and suprarenal 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 it 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 deglu- 

 tition through motor fibers 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 conducting impressions to the medulla, excites the reflex 

 movements of deglutition and respiration ; through the motor fila- 

 ments 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 muscles. 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. 



