608 THE CRANIAL NERVES. 



where the nerve is in contact with the submaxillary gland. Others form a plexus 

 with branches of the hypoglossal nerve at the inner border of the hyo-glossus muscle. 



(6) Branches to the mucous membrane of the mouth are given from the nerve at 

 the side of the tongue, and supply also the gums. Some delicate filaments are like- 

 wise distributed to the substance of the sublingual gland. 



(c) The lingual or terminal branches perforate the muscular structure of the tongue, 

 and divide into filaments, which are continued almost vertically upwards to the conical 

 and fungiform papillae. Near the tip of the tongue the branches of the gustatory and 

 hypoglossal nerves are united. 



INFERIOR DENTAL NERVE. 



The inferior dental nerve is the largest of the three branches of the 

 lower maxillary nerve. It descends under cover of the external pterygoid 

 muscle, behind and to the outer side of the gustatory nerve, and, passing 

 between the ramus of the jaw and the internal lateral ligament of the 

 temporo-maxillary articulation, enters the inferior dental canal. In com- 

 pany with the dental artery, it proceeds along this canal, and supplies 

 branches to the teeth. At the mental foramen it bifurcates ; one part, 

 the incisor branch, being continued onwards within the bone to the 

 middle line, while the other, the much larger labial branch, escapes by the 

 foramsn to the face. 



When about to enter the foramen on the inner surface of the ramus of 

 the jaw, the inferior dental nerve gives off the slender rnylo-hyoid branch. 



(a) The mylo-hyoid branch is lodged in a groove on the inner surface of the ramus 

 of the maxillary bone, in which it is confined by fibrous membrane, and is distributed 

 to the lower or cutaneous surface of the mylo-hyoideus and to the anterior belly of 

 the digastric muscle. This nerve may be traced back within the sheath of the inferior 

 dental to the motor portion of the inferior maxillary nerve. 



(b) The dental branches supplied to the molar and bicuspid teeth correspond to the 

 number of the fangs of those teeth. Each branch enters the minute foramen in the 

 extremity of a fang, and terminates in the pulp of the tooth. Not unfrequently a 

 collateral branch supplies twigs to several teeth. 



(c) The incisor branch has the same direction as the trunk of the nerve : it extends 

 to the middle line from the point of origin of the labial branch, and supplies nerves 

 to the canine and incisor teeth. 



(d) The labial or mental branch emerging from the bone by the foramen on the 

 outer surface, divides beneath the depressor of the angle of the mouth into two 

 parts. 



One of these, the outer division, communicating with the facial nerve, supplies the 

 depressor anguli oris and orbicularis oris muscles, and the integument of the chin. 



The inner portion, the larger of the two, ascends to the lower lip beneath the de- 

 pressor labii inferioris muscle, to which it gives filaments : the greater number of the 

 branches end on the inner and outer surfaces of the lip. These inner branches assist 

 only slightly in forming the plexus of union with the facial nerve. 



OTIC GANGLION. 



The otic ganglion, or ganglion of Arnold, of a reddish grey colour, is 

 situated on the deep surface of the lower maxillary trunk, nearly at the 

 point of junction of the motor fasciculus with that nerve, and around the 

 origin of the internal pterygoid branch. Its inner surface is close to the 

 cartilaginous part of the Eustachian tube and the circumflexus palati 

 muscle ; and behind it is the middle meuingeal artery. 



Connection with nerves roots. The ganglion is connected with the 

 lower maxillary nerve, especially with the branch furnished to the internal 

 pterygoid muscle, and with the auricnlo-teinporal nerve, and thus obtains 

 motor and sensory roots ; it is brought into connection with the sympa- 



