292 THE NERVOUS SYSTEM 



surface of the stomach, and those from the right to the pos- 

 terior ; the right vagus is also distributed to the liver, spleen, 

 kidneys and entire small intestine. 



Throughout its whole course the pneumogastric communi- 

 cates with other nerves, especially the sympathetic. 



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, receiving 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 phe- 

 nomena of deglutition. The superior laryngeal branches, 

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

 roids. 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 deglu- 

 tition. 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 em- 

 barrassed phonation, though the fibers thus influencing the 

 vocal sounds come to the recurrent laryngeal from the spinal 

 accessory. The uses of the cardiac branches have been no- 

 ticed under discussion of the heart's action. The pulmonary 

 branches are both motor and sensory and go to the lower 

 trachea, the bronchi and lung substance. Section of the 

 tenth destroys the sensibility of the mucous membrane of 

 the trachea and bronchi and the contractile power of the 

 muscular fibers of the tubes. The esophageal branches are 

 mixed, though motor fibers predominate. Food will not pass 



