Newous System. 545 



both of which it anastomoses freely. It passes through the skull by way of the stylo- 



mastoid foramen, a hole in the temporal bone of the skull. 

 Eighth pair is the Auditory, sometimes railed the portio mollis of the seventh pair. 



t is purely sensory, conveying to the brain those agitations of the organs in the ear tli.it 

 to make up the sensation of sound. In the ear it divides into two brandies, one oi 

 which runs up the modiolus of the cochlea and distributes fibres to the four 

 thousand arches of corti, and the other goes to the vestibule and distributes its terminal 

 fibres to the semicircular canals, the auditory filaments of the crista acustica, and the 

 otoliths. (Chapter 48.) This nerve connects with the brain by two roots, which em- 

 brace the restiform body, and originate in the floor and sides of the fourth ventricle and 

 in the restiform body. 



The ninth pair is the Glosso Pharyngeal. This nerve also originates in the restiform 

 ganglion. It is sensori motor, but chiefly sensory, sending branches to the tongue, which 

 convey thence both touch and taste sensations, and also controlling some of the muscles 

 of that organ. It also has branches to the pharynx, and sensory touch fibres to the ex- 

 ternal canal of the ear. It leaves the brain by way of the posterior foramen lacerum, a 

 hole at the junction between the occipital and temporal bones. 



Tenth pair is the Pneumogastric, or Par Vagum. It is both sensory and motor. It 

 arises from the restiform body, near the olivary body, and passes through the jugular 

 foramen, 1 in the base of the skull, in company with the glosso pharyngeal and spinal 

 accessory, the ninth and eleventh pairs. It runs down the neck, and alongside of the 

 03sophagus through the diaphragm and into the stomach. Branches go to the pancreas, 

 liver, gall-bladder, and duodenum, &c. Other branches go to the larynx, pharynx, heart, 

 and lungs. It anastomoses in the neck with the spinal glosso pharyngeal, hypoglossal 

 and great sympathetic nerves. 



The eleventh pair is the spinal accessory. This nerve does not originate in the skull 

 at all, but from the spinal cord about the fourth or fifth cervical vertebra, by fibres which 

 issue from between the anterior and posterior roots of the cervical nerves. It runs up 

 the cord and into the cranium through the great foramen, and leaves it in company with 

 the par vagum and the glosso pharyngeal and the jugular vein, through the jugular for- 

 amen. It is called the accessory of the par vagum, because the two taken together form 

 a pair resembling a pair of spinal nerves, the par vagum with its ganglion being con- 

 sidered the posterior, or afferent, and the accessory the anterior or motor. This nerve 

 loses itself in the trapezius 2 muscle. 



Twelfth pair. This is the Lingual or Hypoglossal nerve. It arises by ten or twelve 

 very fine filaments from the grooves which separate the pyramidal from the olivary 

 bodies, and some of the filaments are traced from the olivary ganglion. It passes from 

 the cranium through the anterior condyloid foramen in the base of the occipital bone of 

 the skull. It furnishes branches to several of the muscles of the neck, and the main 

 stem gives its filaments to the muscles of the tongue and pharynx. It is a motor nerve. 



The Sympathetic System is next to be mentioned. It consists essentially of two great 

 cords, one on each side in front, or on the inferior side of the spinal column, and extend- 

 ing from the cranium to the coccyx. (See fig. 262.) These two cords start from a com' 

 mon point in the ganglion of Ribes, which lies near the corpus callosum in the middle 

 of the brain, thence they diverge; each one passes with the carotid artery of its side, 

 through the carotid canal in the temporal bone, and thence on down by the side of the 

 spine through the neck, forming three neck ganglia, called the superior, the middle, or 

 thyroid, and the inferior or vertebral ganglion ; thence down the trunk, forming twelve 

 thoracic ganglia, one for each of the dorsal vertebra ; thence through the loins, forming 

 five lumbar ganglia; and below these three or four sacral ganglia ; and at the coccyx, 

 where the pair come together again, is formed a final small ganglion, the coccygeal. 

 Thus the two homologous sides of the system are united at the two ends, head and tail. 



From each of the ganglions above mentioned, a branch connects with the spinal 

 nerves. There are also branches and some small ganglia connecting with the cranial 

 fierves. There are three principal plexuses formed in connection with the sympathetic, 

 which minister to the viscera of the chest and abdomen. These are the cardiac, solar, 

 and hypogastric plexuses. The great cardiac plexus is situated opposite the third dorsal 

 vertebra, at the point where the bronchial tubes branch off from the windpipe. It is 

 formed by the union of the middle and inferior cardiac nerves, which, in turn, are 

 formed by the convergence and union of fibres from the cervical ganglia. The great 

 cardiac plexus also receives fibres from the first thoracic ganglion, the pneumogastric 



1 Also called the foramen lacerum posterius. 



2 A muscle at the posterior part of the neck and shoulder which elevates the shoulder, 

 depresses it, or sarries it back, according as one or other set of fibres is contracted. 



