596 INFERIOR MAXILLARY DIVISION. 



through the foramen spinosum, and, along with the nerve of the same name from 

 the II. division, supplies sensory fibres to the dura mater. Fibres proceed from it 

 through the petroso-squamosal fissure to the mucous membrane of the cells of the 

 mastoid process. 



2. Motor fibres for the muscles of mastication, viz., the masseteric, the two deep 

 temporal nerves, and the internal and external pterygoid nerves. The sensory 

 fibres for the muscles are supplied by the sensory fibres. 



3. The buccinator is a sensory nerve for the mucous membrane of the cheek, 

 and the angle of the mouth as far as the lips. 



According to Jolyet and Laffont, it contains, in addition, vaso-motor fibres for the mucous 

 membrane of the cheek, lower lip, and their mucous glands ; but these fibres are probably 

 derived from the sympathetic 



Trophic Fibres. As this region of the mucous membrane of the mouth ulcerates after section 

 of the trigeminus, soriie have supposed that the buccinator nerve contains trophic fibres. But, 

 as Rollett pointed out, section of the inferior maxillary nerve paralyses the muscles of mastica- 

 tion on the same side, and hence the teeth do not act vertically upon each other, but press 

 against the cheek. Owing to the loss of the sensibility of the mouth, food passes between the 

 gum and the cheek, where it may remain attached, undergo decomposition, and perhaps 

 chemically irritate the mucous membrane. At a later stage, owing to the wearing away of the 

 teeth in an oblique manner, ulcers begin to form on the sound side. Hence, there is no necessity 

 for assuming the existence of trophic fibres in this nerve. After section of the trigeminus, the 

 nasal mucous membrane on the same side becomes red and congested. This is due to the fact 

 that dust or mucus, not being removed from the nose by the usual reflex acts, remains there, 

 irritates, and ultimately causes inflammation. 



4. The lingual (k) receives at an acute angle the chorda tympani (i i), a branch 

 of the facial coming from the tympanic cavity. The lingual does not contain any 

 motor fibres ; it is the sensory and tactile nerve of the anterior two-thirds of the 

 tongue, of the anterior palatine arch, the tonsil, and the floor of the mouth. These, 

 as well as all the other sensory fibres of the mouth, when stimulated, cause a reflex 

 secretion of saliva (compare 145). The lingual is accompanied by the nerve of 

 Uiste (chorda) for the tip and margins of the tongue (i.e., the parts not supplied by 

 the glossopharyngeal). After section of the lingual nerve in man, Busch, Inzani, 

 and Lusanna found that the tactile sensibility was lost in the half of the tongue, 

 and there was loss of taste in the anterior part [two-thirds] of the tongue. The 

 fibres which administer to the sense of taste do not as a rule belong to the lingual 

 itself, but are derived from the chorda tympani (p. 600). According to Schiff, the 

 lingual nerve is the gustatory nerve, and some cases of Erb and Senator support 

 this view. Such cases, however, seem to be exceptions to the general rule. The 

 lingual nerve in the substance of the tongue is provided with small ganglia 

 (Remah, Stirling). Schiff observed that section of the lingual (and also of the 

 hypoglossal) caused redness of the tongue, so that vaso-motor fibres are present in 

 its course. It is unknown whether these are derived from the anastomoses of the 

 Gasserian ganglion with the sympathetic. The lingual appears to receive vaso- 

 dilator fibres from the chorda for the tongue and gum ( 349). 



After section of the trigeminus, animals frequently bite their tongue, as they cannot feel the 

 position and movements of this organ in the mouth. 



5. The inferior dental is the sensory branch to the teeth and gum ; the vaso- 

 motor fibres reach it from the superior cervical ganglion. Before it passes into the 

 canal in the lower jaw, it gives off the mylo-hyoid nerve, which supplies motor 

 fibres to the mylo-hyoid and the anterior belly of the digastric, and also some fibres 

 to the triangularis menti and the platysma ; the muscular sensory nerves also lie 

 in these branches. The mental nerve, which issues from the mental foramen, is the 

 sensory nerve for the chin, lower lip, and the skin at the margin of the jaw. 



6. The auriculotemporal gives sensory branches to the anterior wall of the 

 external auditory meatus, the tympanic membrane, the anterior part of the ear, 

 the adjoining region of the temple, and to the maxillary articulation. 



