518 NERVOUS SYSTEM 



SUBLINGUAL (TWELFTH NERVE) 



The last of the motor cranial nerves is the sublingual ; and its action 

 is intimately connected with the physiology of the tongue in deglutition 

 and articulation, although the sublingual is also distributed to certain of 

 the muscles of the neck. 



Physiological Anatomy. The apparent origin of the sublingual is 

 from the bulb, in the groove between the olivary body and the anterior 

 pyramid, on the line of the anterior roots of the spinal nerves. At this 

 point its root is formed of ten to twelve filaments, which extend from 

 the inferior portion of the olivary body to about the junction of the 

 upper with the middle third of the bulb. These filaments of origin are 

 separated into two groups, superior and inferior. From this apparent 

 origin, the filaments have been traced into the gray matter of the floor 

 of the fourth ventricle, between the deep origin of the pneumogastric 

 and the glosso-pharyngeal. It is probable that some of the filaments of 

 origin of these nerves decussate in the floor of the fourth ventricle. 

 The superior and inferior filaments of origin of the nerve unite to form 

 two bundles, which pass through distinct perforations in the dura mater. 

 These two bundles then pass into the anterior condyloid foramen and 

 unite into a single trunk as they emerge from the cranial cavity. 



After the sublingual has passed out of the cranial cavity it anasto- 

 moses with several nerves. It sends a filament of communication to 

 the sympathetic as it branches from the superior cervical ganglion. 

 Soon after it has passed through the foramen it sends a branch to the 

 pneumogastric. It anastomoses by two or three branches with the 

 upper two cervical nerves, the filaments passing in both directions 

 between the nerves. It anastomoses with the lingual branch of the 

 fifth by two or three filaments passing in both directions. 



In its distribution the sublingual presents several peculiarities : 



Its first branch, the decendens noni, passes down the neck to the 

 sterno-hyoid, sterno-thyroid and omo-hyoid muscles. 



The thyro-hyoid branch is distributed to the thyro-hyoid muscle. 



The other branches are distributed to the -stylo-glossus, hyo-glossus, 

 genio-hyoid and genio-hyo-glossus muscles, their terminal filaments going 

 to the intrinsic muscles of the tongue. 



It is thus seen that the sublingual nerve is distributed to all the 

 muscles in the infra-hyoid region, the action of which is to depress the 

 larynx and the hyoid bone after the passage of the alimentary bolus 

 through the pharynx ; to one of the muscles in the supra-hyoid region, 

 the genio-hyoid ; to most of the muscles that move the tongue ; and to 



