THE CRANIAL NERVES 2QI 



branches ot the sympathetic and pass to the deep cardiac plexus. 

 (3) In the thorax it gives off (a) thoracic cardiac branches, 

 which pass to the deep cardiac plexus ; (b) anterior pulmonary 

 branches, which go to the roots of the lungs in front; (c) pos- 

 terior pulmonary branches, which go to the roots of the lungs 

 behind and send some filaments to the pericardium; filaments 

 from (b) and (c) follow the air passages through the lungs; (d) 

 esophageal branches, which unite with fibers from the opposite 

 nerve to form the esophageal plexus. (4) In the abdomen are 

 the gastric branches ; those from the left nerve are distributed 

 to the anterior surface of the stomach, and those from the right 

 to the posterior; the right vagus is also distributed to the liver, 

 spleen, kidneys and entire small intestine. 



Throughout the whole course of the pneumogastric commun- 

 ication with other nerves, especially the sympathetic, is very free. 



Functions. The root of the tenth in the medulla is purely 

 sensory, but the nerve communicates with at least five motor 

 nerves, and is distributed to mucous membranes and to voluntary 

 and involuntary muscle tissue. The auricular branches contain 

 both motor and sensory fibers, and their function is indicated in 

 their distribution. The pharyngeal branches are mixed, re- 

 ceiving motor filaments from the spinal accessory. Sensibility 

 is supplied to the pharynx not by this nerve alone, but by the 

 branches of the fifth and probably of the ninth; indeed it seems 

 that the pharyngeal branches of the tenth have little to do with 

 the reflex phenomena of deglutition. The superior laryngeal 

 branches, mainly sensory, supply also motor power to the crico- 

 thyroids. Stimulation of the filaments of these branches pre- 

 vents the entrance of foreign bodies into the larynx by reflex 

 closure of the glottis, and also excites movements of deglutition. 

 Their section produces hoarseness. The recurrent, or inferior 

 laryngeal, branches, chiefly motor, supply the muscular tissue 

 of the upper esophagus and trachea, as well as the muscles of the 

 larynx. Section of them causes embarassed phonation, though 



