292 THE NERVOUS SYSTEM 



the fibers thus influencing the vocal sounds come to the recur- 

 rent laryngeal from the spinal accessory. The uses of the car- 

 diac branches have been noticed 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 mem- 

 brane 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 

 readily into the stomach -on section of the tenth because of the 

 absence of muscular contractions in the esophagus. 



Influence of the Vagus on Respiration. Section of both 

 these nerves temporarily increases the number of respirations, 

 which soon, however, become exceedingly slow until death 

 ensues. Inspiration is very profound indeed so profound as to 

 produce rupture of some of the pulmonary capillaries with con- 

 sequent hemorrhage and coagulation of the blood and consolida- 

 tion of the lung in part or whole. Section of only one of the vagi 

 is not usually followed by death. Further notice of the relation 

 of the pneumogastric to respiration is given elsewhere. 



Influence of Vagus on the Stomach, Intestine and Liver. 

 Stimulation of the pneumogastric causes contraction of the stom- 

 ach; but since the contraction is not immediate, the impulse is 

 probably carried to it by fibers of the sympathetic running 

 with the gastric branches of the tenth. When the vagus is cut 

 during digestion in the stomach the contractions of the muscular 

 wall are impaired and the sensibility of the organ is abolished. 

 Secretion is interfered with, but not stopped. 



Section of the vagus seems also to impair intestinal secretion 

 and movements, but it is not improbable that this is because 

 sympathetic fibers joining the vagus high in the neck are dis- 

 tributed with it to the intestine. 



Simple division of the pneumogastrics inhibits the formation 

 of glycogen in the liver; but when the central ends of the cut 



