THE CRANIAL NERVES. 607 



filaments from the first and second cervical nerves, the sympathetic and 

 vagus. It is finally distributed to the intrinsic muscles of the tongue and to 

 the genio-hyo-glossus, hyo-glossus, and stylo-hyoid muscles. Branches 

 derived from the cervical plexus pass to muscles which elevate and depress 

 the hyoid bone. (Fig. 282.) 



Cortical Connections. The hypoglossal nerve nuclei are connected 

 with nerve-cells in the lower third of the general motor area around the in- 

 ferior termination of the fissure of Rolando by axons which descend in the 

 pyramidal tract. 



Properties. Faradization of the nerve gives rise to convulsive move- 

 ments of the muscles to which it is distributed. Division of the nerve is 

 followed by a loss of motion and an interference with deglutition, mastication, 

 and articulation, especially in the pronunciation of the consonantal sounds. 

 In hemiplegia, complicated with paralysis of the tongue from injury to the 

 hypoglossal tract, the opposite side of the tongue is involved in the paralysis. 

 On protrusion of the tongue the tip is deviated to the paralyzed side, due to 

 the unopposed action of the muscle of the opposite side. 



Function. The hypoglossal nerve transmits nerve impulses from its 

 origin to the intrinsic and extrinsic muscles of the tongue, exciting them to 

 activity. The coordinate activity of these muscles favorably assists mastica- 

 tion, articulation, and deglutition. 



