562 NERVOUS SYSTEM. 



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 medulla oblongata, 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 medulla. These filaments of origin are sepa- 

 rated 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. Although there is much difference of opinion upon this point, 

 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 ante- 

 rior 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 anastomoses 

 with several nerves. It sends a filament of communication to the sympa- 

 thetic 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 descendens 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 of the mus- 

 cles 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 which move the tongue ; and to the muscular fibres 

 of the tongue itself. The action of these muscles and of the tongue itself in 

 deglutition has already been fully discussed. 



Properties and Uses of the Sublingual. The fact that the sublingual 

 nerve arises from a continuation of the motor tract of the spinal cord ^and 

 has no ganglion upon its main root would lead to the supposition that it is 

 an exclusively motor nerve. In operating upon the roots of the spinal acces- 

 sory when the origin of the sublingual is necessarily exposed Longet has 

 irritated the roots in the dog, without any evidence of pain on the part of 



