pterygoid muscle and the pharynx, next between the two pterygoid muscles, then between the internal pterygoid and ramus of the jaw, and between the stylo-glossus muscle and the submaxillary gland; lastly, it runs along the side of the tongue, resting against the hyo-glossus muscle and crossing the duct of the submaxillary gland, and is covered in by the mylo-hyoideus and mucous membrane. The gustatory nerve, while between the pterygoid muscles, often receives a communicating branch from the inferior dental; lower down it is joined at an acute angle by the chorda tympani, a small nerve which, arising from the facial in the aquæductus Fallopii, crosses the tympanum, and escapes from that cavity through the fissura Glaseri. Having joined the gustatory nerve, the chorda tympani is continued downwards in its sheath to the submaxillary ganglion. One or two branches are given by the gustatory nerve to the submaxillary ganglion. On the hyo-glossus muscle several branches of communication join with branches of the hypoglossal nerve, and others are sent to the sublingual gland, Wharton's duct, and mucous membrane of the mouth and gums. SIXTH PAIR. ABDUCENTES. -The abducens nerve, about half the size of the motor oculi, arises by several filaments from the upper constricted part of the corpus pyramidale, and by a few fibres from the pons Varolii. Proceeding forwards from this origin, it lies parallel with the basilar artery, and, piercing the dura mater on the clivus Blumenbachii of the sphenoid bone, ascends between the two layers of that membrane to the cavernous sinus. It then runs forwards through the sinus below the level of the other nerves, and resting against the internal carotid artery, to the sphenoidal fissure. Entering the orbit through the sphenoidal fissure it passes between the two heads of the external rectus, and is distributed to that muscle. At the sphenoidal fissure it lies upon the ophthalmic vein, from which it is separated by a lamina of dura mater; and in the cavernous sinus is joined by several filaments from the carotid plexus. Mayo traced the deep origin of this nerve between the fasciculi of the corpora pyramidalia to the posterior part of the medulla oblongata; and it appears to arise from the gray substance of the fourth ventricle. SEVENTH PAIR. The seventh pair of nerves, of Willis, consists of two nervous cords 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 the auditory nerve or portio mollis.' The facial FACIAL NERVE; portio dura; SEVENTH PAIR of Soemmering. nerve, the motor nerve of the face, arises from the upper part of the groove between the corpus olivare and corpus restiforme close to, and by a few fibres from, the pons Varolii; its deep origin being traced through the corpus restiforme to the side of the floor of the fourth ventricle. The nerve passes forwards, resting on the crus cerebelli, and comes into relation with the auditory nerve, with which it enters the meatus auditorius internus, lying at first to the inner side of, and then upon that nerve. At the bottom of the meatus, the facial nerve enters A third nerve of small size, portio intermedia of Wrisberg, is brought into view by separating these two cords. The researches of Morganti render it probable that the portio intermedia is connected, at its origin in the corpus restiforme, with the auditory nerve; that it is the posterior or sensitive root of the facial; that the intumescentia gangliformis of the facial is the ganglion of this root; that it bestows the principal part of the sensitive function on the facial; and that the chorda tympani is partly derived from the intumes centia gangliformis. the aquæductus Fallopii, and takes its course forwards to the hiatus Fallopii, in the anterior wall of the petrous bone, where it forms a gangliform swelling (intumescentia gangliformis, ganglion geniculare), and receives the petrosal branch of the Vidian nerve. It then curves backwards towards the tympanum, and descends in the inner wall of that cavity to the stylo-mastoid foramen. Emerg ing at the stylo-mastoid foramen, it passes forwards within the parotid gland, crossing the external carotid artery, to the ramus of the lower jaw, were it splits into two trunks, temporo-facial and cervico-facial. These trunks divide into numerous branches, which escape from the anterior border of the parotid gland, and are distributed in a radiated manner over the side of the face, from the temple to below the lower jaw; on the masseter muscle the branches communicate and form loops, and the whole arrangement over the side of the face has been termed pes anserinus. In the meatus auditorius, the facial nerve communicates with the auditory nerve by one or two filaments; the intumescentia gangliformis receives the nervus petrosus superficialis major and minor, and sends a twig back to the auditory nerve; behind the tympanum, the nerve receives one or two twigs from the auricular branch of the pneumogastric; at its exit from the stylo-mastoid foramen it receives a twig from the glosso-pharyngeal, and in the parotid gland one or two large branches from the auriculo-temporal nerve. Besides these, the facial nerve has numerous peripheral communications, with the branches of the fifth nerve on the face, with the cervical nerves in the parotid gland and on the neck, and with the sympathetic. The numerous communications of the facial nerve have obtained for it the designation of nervus sympatheticus minor. The Branches of the facial nerve are Within the aquæductus Fallopii After emerging at the stylo-mastoid On the face. Tympanic, Digastric. The Tympanic branch is a small filament given off by the facial while in the petrous bone, and distributed to the stapedius muscle. The Chorda tympani quits the facial immediately above the stylo-mastoid foramen, and ascends by a distinct canal to the upper part of the posterior wall of the tympanum, where it enters that cavity through an opening situated between the base of the pyramid and the attachment of the membrana tympani, and becomes invested by mucous membrane. It then crosses the tympanum between the handle of the malleus and long process of the incus to its anterior inferior angle, and escapes through an opening in the fissura Glaseri, to join the gustatory nerve at an acute angle between the two pterygoid muscles. Inclosed in the sheath of the gustatory nerve, it descends to the submaxillary gland, where it enters the submaxillary ganglion. The Posterior auricular branch ascends behind the ear, between the meatus and mastoid process, and divides into an anterior or auricular, and a posterior or occipital, branch. The auricular branch receives a filament of communica tion from the auricular branch of the pneumogastric nerve, and distributes fila ments to the retrahens aurem muscle and pinna. The occipital branch com municates with the auricularis magnus and occipitalis minor, and is distributed to the occipital portion of the occipito-frontalis. The Stylo-hyoid branch is distributed to the stylo-hyoid muscle, and commu nicates with the sympathetic plexus of the external carotid artery. The Digastric branch supplies the posterior belly of the digastricus muscle, and communicates with the glosso-pharyngeal and pneumogastric nerve. FIG. 265. DISTRIBUTION OF THE FACIAL NERVE AND BRANCHES OF THE CERVICAL PLEXUS. 1. Facial nerve, escaping from the stylomastoid foramen, and crossing the ramus of the lower jaw: the parotid gland has been removed in order to see the nerve distinctly. 2. Posterior auricular branch; the digastric and stylo-hyoid twigs are seen near the origin of this branch. 3. Temporal branches, communicating with (4) branches of the supraorbital nerve. 5. Infraorbital branches, communicating with (6) the infraorbital nerve. 7. Supra-maxillary branches, communicating with (8) the mental nerve. 9. Inframaxillary branches communicating with (10) the superficialis colli nerve, and forming a plexus (11) over the submaxillary gland. The distribution of the branches of the facial in a radiated direction over the side of the face and their looped communications constitute the pes anserinus. 12. Auricularis magnus nerve, one of the ascending branches of the cervical plexus. 13. Occipitalis minor ascending along the posterior border of the sterno mastoid. 14. Superficial and deep descending branches of the cervical plexus. 15. Spinal accessory nerve, giving off a branch to the external surface of the trapezius muscle. 16. Occipitalis major nerve, the posterior branch of the second cervical. The TEMPORO-FACIAL DIVISION, while in the parotid gland, sends a branch of communication along the carotid artery to the auriculo-temporal nerve, and divides into temporal, malar, and infraorbital branches. The Temporal branches ascending upon the temporal region supply the attrahens aurem, occipito-frontalis, and orbicularis palpebrarum; and communicate with the supraorbital nerve and temporal branch of the superior maxillary. The Malar branches cross the malar bone to the outer angle of the eye, and supply the orbicularis palpebrarum, corrugator supercilii, and eyelids. They communicate with the subcutaneus malæ branch of the superior maxillary nerve, and with branches of the ophthalmic nerve in the eyelids. The Infraorbital branches cross the masseter muscle, and are distributed to the buccinator, elevator muscles of the upper lip and orbicularis oris. They communicate with the terminal branches of the infraorbital nerve, infra-trochlear and nasal nerve. Two or more of these branches are found by the side of Stenon's duct. The CERVICO-FACIAL DIVISION, smaller than the temporo-facial, communicates in the parotid gland with the auricularis magnus nerve, and divides into branches which admit of arrangement into three sets; buccal, supra-maxillary, and infra-maxillary. The Buccal branches pass forwards across the masseter muscle towards the mouth, and distribute branches to the orbicularis oris and buccinator. They communicate with branches of the temporo-facial, and with the buccal branch of the inferior maxillary nerve. The Supra-maxillary branches are destined to the muscles of the lower lip, and take their course along the body of the lower jaw. Beneath the depressor anguli oris, they have a plexiform communication with the inferior dental nerve. The Infra-maxillary branches (subcutanei colli) take their course below the lower jaw, pierce the deep cervical fascia, and are distributed to the platysma; communicating with the superficialis colli nerve. [FIG. 266. AUDITORY NERVE; portio mollis; EIGHTH PAIR of Soemmering.-The auditory nerve takes its origin in the lineæ transversæ (striæ medullares) of the anterior wall or floor of the fourth ventricle, and winds around the corpus restiforme, from which it receives fibres, to the posterior border of the crus cerebelli. It then passes forwards on the crus cerebelli in company with the facial nerve, which lies in a groove on its superior surface, enters the meatus auditorius internus, and at the bottom of the meatus divides into two branches, cochlear and vestibular. The auditory nerve is soft and pulpy in texture, and receives in the meatus auditorius several filaments from the facial nerve. EIGHTH PAIR of Willis; ninth, tenth, and eleventh pairs of Soemmering; con ORIGIN AND DISTRIBUTION OF THE PORTAO MOLLIS of the seventh pair, or auditory nerve. 1. The medulla oblongata. 2. The pons Varolii. 3 and 4. The crura cerebelli sists of three nerves, glosso-pharyngeal, of the right side. 5. Eighth pair. 6. Ninth pneumogastric, and spinal accessory. pair. 7. The auditory nerve distributed to the labyrinth. 8. The sixth pair. 9. The portio dura of the seventh pair. 10. The fourth pair. 11. The third pair.] GLOSSO-PHARYNGEAL NERVE. - The glosso-pharyngeal nerve, as its name implies, is the nerve of sensation of the mucous membrane of the tongue and pharynx, but it also gives branches to some of the muscles of these organs. It arises by five or six filaments from the groove between the corpus olivare and restiforme, or rather from the anterior border of the latter, and escapes from the skull at the innermost extremity of the jugular foramen through a distinct opening in the dura mater, lying anteriorly to the sheath of the pneumogastric and spinal accessory nerve, and internally to the jugular vein. It then passes forwards between the jugular vein and internal carotid artery, and crosses the artery to reach the posterior border of the stylopharyngeus. Following the posterior border of this muscle for a short distance, it next passes across it and the middle constrictor and behind the hyo-glossus muscle, to be distributed to the mucous membrane of the tongue, pharynx, and tonsil. While in the jugular fossa, the nerve presents two gangliform swellings; one superior, the ganglion jugulare (Müller), of small size, and involving only the posterior fibres of the nerve; the other inferior, nearly half an inch below the preceding, of larger size, and occupying the whole diameter of the nerve, the ganglion petrosum or ganglion of Andersch.' The fibres of origin of this nerve may be traced through the fasciculi of the corpus restiforme to the gray substance of the floor of the fourth ventricle. 1 Charles Samuel Andersch. Humani Aliquibus, 1797." "Tractatus Anatomico-Physiologicus de Nervis corporis The branches of the glosso-pharyngeal nerve are branches of communication and branches of distribution. The Branches of communication proceed chiefly from the ganglion of Andersch; they are, one to join the auricular branch of the pneumogastric; one to the ganglion of the pneumogastric; one to the superior cervical ganglion of the sympathetic; and one, which arises below the ganglion and pierces the posterior belly of the digastricus muscle, to join the facial nerve. The Branches of distribution are Tympanic, Pharyngeal, Tonsillitic, Lingual. The Tympanic branch (Jacobson's nerve) proceeds from the ganglion of Andersch, or from the trunk of the nerve immediately above the ganglion; it enters a small bony canal in the jugular fossa (page 66), and divides into six branches, which are distributed on the inner wall of the tympanum, and establish a plexiform communication (tympanic plexus) with the sympathetic and fifth pair of nerves. The branches of distribution supply the fenestra rotunda, fenestra ovalis, and Eustachian tube; those of communication join the carotid plexus in the carotid canal, the petrosal branch of the Vidian nerve, and the otic ganglion. The Carotid branches are several filaments which follow the trunk of the internal carotid artery, and communicate with the nervi molles of the sympathetic. The Muscular branch divides into filaments, which are distributed to the posterior belly of the digastricus, stylo-hyoideus, stylo-pharyngeus, and constrictor muscles. The Pharyngeal branches are two or three filaments which are distributed to the pharynx and unite with the pharyngeal branches of the pneumogastric and sympathetic nerve to form the pharyngeal plexus. The Tonsillitic branches proceed from the glosso-pharyngeal nerve, near its termination; they form a plexus (circulus tonsillaris) around the base of the tonsil, from which numerous filaments are given off to the mucous membrane of the fauces and soft palate. These filaments communicate with the descending palatine branches of Meckel's ganglion. The Lingual branches enter the substance of the tongue beneath the hyoglossus and stylo-glossus muscle, and are distributed to the mucous membrane of the side and base of the tongue, and to the epiglottis and fauces. PNEUMOGASTRIC or VAGUS NERVE ; par vagum; TENTH PAIR of Soemmering. -The pneumogastric is the nerve of the respiratory organs and upper part of the alimentary canal, supplying branches to the larynx, trachea, lungs, pharynx, oesophagus, and stomach, and also giving branches to the heart. It arises by ten or fifteen filaments from the groove between the corpus olivare and corpus restiforme, or rather from the anterior border of the latter, immediately below the glosso-pharyngeal, and passes out of the skull through the inner extremity of the jugular foramen, inclosed in a sheath of dura mater common to it and the spinal accessory. The nerve then takes its course down the side of the neck, lying at first between the internal jugular vein and internal carotid artery, and lower down behind and between that vein and the common carotid artery, and inclosed in the same sheath. At the root of the neck the course of the nerve on the two sides is different. The right nerve enters the chest by passing between the subclavian artery and vein, and descends by the side of the trachea to the posterior part of the root of the right lung; it then proceeds as a double cord along the posterior aspect of the oesophagus to the corresponding side of the stomach; the two cords reuniting at the lower part of the oesophagus. The |