444 AURICULAR NERVE. ABDUCENS. 



The inferior dental nerve gives off but one branch, the mylo-hyoidean, 

 which leaves the nerve just as it is about to enter the dental foramen. 

 This branch pierces the insertion of the internal lateral ligament, and 

 descends along a groove in the bone to the inferior surface of the rnylo- 

 hyoid muscle, to which, and to the anterior belly of the digastricus, it 

 is distributed. 



The ANTERIOR AURICULAR NERVE originates by two roots, be- 

 tween which the arteria meningea media takes its course, and passes 

 directly backwards behind the articulation of the lower jaw, against 

 which it rests. In this situation it divides into two branches, which 

 reunite, and form a kind of plexus. From the plexus two branches 

 are given off ascending and descending. The ascending or temporal 

 branch sends one or two considerable branches of communication to the 

 facial nerve, and then ascends in front of the ear to the temporal re- 

 gion, upon which it is distributed in company with the branches of the 

 temporal artery. In its course it sends filaments to the temporo-max- 

 illary articulation, to the pinna and meatus of the ear, and to the in- 

 tegument in the temporal region. It communicates on the temple with 

 branches of the facial, supra -orbital, lachrymal, and subcutaneus 

 malae nerve. The descending branch enters the parotid gland, to which 

 it sends numerous branches ; it communicates with the inferior dental 

 and auricularis magnus nerve, and supplies the external ear, the mea- 

 tus auditorius, and the temporo-maxillary articulation, and sends one 

 or two filaments into the tympanum. 



SIXTH PAIR. ABDUCENTES. The abducens nerve, about half the 

 size of the motor oculi, arises by several filaments from the upper con- 

 stricted part of the corpus pyramidale close to the pons Varolii. 

 Proceeding forwards from this origin it lies parallel with the basilar 

 artery > and, piercing the dura mater upon the clivus Blumenbachii of 

 the sphenoid bone, ascends beneath that membrane to the cavernous 

 sinus. It then runs forwards along the inner wall of the sinus below 

 the other nerves, and, resting against the internal carotid artery, 

 passes between the two heads of the external rectus, and is distributed 

 to that muscle. As it enters the orbit, it lies upon the ophthalmic vein, 

 from which it is separated by a lamina of dura mater. In the cavern- 

 ous sinus it is joined by several filaments from the carotid plexus, by 

 one from Meckel's ganglion, and one from the ophthalmic nerve. Mr. 

 Mayo traced the origin of this nerve between the fasciculi of the cor- 

 pora pyramidalia to the posterior part of the medulla oblongata ; and 

 Mr. Grainger pointed out its connection with the grey substance of the 

 spinal cord. 



SEVENTH PAIR. The seventh pair consists of two nerves which lie 

 side by side on the posterior border of the crus cerebelli. The smaller 

 and most internal of these, and, at the same time, the most dense in 

 texture, is the facial nerve or portio dura. The external nerve, which 

 is soft and pulpy, and often grooved by contact with the preceding, is 



