GLOSSO - PHARYNGEAL NERVE (nervus glos.so-pharyugeus; part of the sixth pair of Galen and the older anatomists ; part of the eighth pair of Willis ; the ninth pair of Soemmerring and some of the modern anato mists). The glosso-pharyngeal, par vagum, and spinal accessory nerves were long considered as forming a single nerve. Willis first clearly pointed out the origin and course of the spinal accessory, separated it from the par vagum, and termed it the nervus accessorius. The glosso pharyngeal appears to have been generally de scribed at the time of Willis as a branch of the par vagum. The term glosso-pharyngeal was not applied to it until the time of Huber.* Previous to the time of Willis, however, some anatomists, more particularly Fallopius,t Eu stachius,*Baubinus,-1- had shown that this nerve was really not a mere branch of the par vagum. The same thing was stated, more or less strongly, by many subsequent anatomists, more particu larly by Winslow,t Ilaller,§ and Vicq D'Azyr.II Soeinmerringli and Andersch** were, how ever, the first who fairly separated the glosso pharyngeal from the par vagum, and ranked it as a distinct nerve. The glosso-pharyngei form the ninth pair of Soemmerring's classification of the encephalic nerves, and were termed the eighth pair by Andersch. There can be no doubt that if we adopt the numerical method of naming these nerves, the glosso-pharyngei properly form the ninth pair. To avoid, how ever, all the misunderstanding which is apt to arise from the use of numerical names when applied to these nerves, the best designa tion for the nerve at present under our conside ration is the glosso-pharyngeal, derived from its being principally distributed upon the tongue and the pharynx. I need scarcely state that, under the term eighth pair, as it is most gene rally used in modern writings, is included the glosso-pharyngeal, par vagum, and spinal ac cessory nerves.t Origin.—The glosso-pharyngeal nerve arises by from two to six filaments from the restiform body of the medulla oblongata, closely upon the groove which separates the restiform from the olivary. body. At its origin it is placed im mediately above and in the same line with the par vagum nerve, and between it and the portio dura of the seventh pair. Its lower margin is generally separated from the upper margin of the par vagum by a few small bloodvessels.
From its origin it first proceeds outwards along with the par vagum and spinal accessory to reach the foramen lacerum posterius. Through the anterior and inner part of this foramen it escapes from the interior of the cra nium, and is enclosed in a strong and separate sheath furnished by the dura mater.:: In its passage through the foramen lacerum it is placed anterior to the par vagum and spinal accessory and the commencement of the inter nal jugular vein, which lie in the order here enumerated. As the nerve issues from the lower part of the footmen lacerum it forms a small rounded chord, close to, but still quite separate from the par vagum, and is situated between the internal jugular vein and internal carotid artery. It now leaves the trunk of the par vagum, proceeds downwards, inwards, and forwards, passing in front of the internal carotid artery and behind the styloid muscles, and joins itself to the stylo-pharyngeus muscle. It runs at first along the lower margin of this muscle, and rests on the superior constrictor of the pharynx which separates it from the tonsil ; it then mounts on the anterior surface of the stylo-pharyngeus muscle, and passes be tween it and the stylo-glossus to reach the base of the tongue, upon which it is ultimately dis tributed. Occasionally, instead of turning over
the lower edge of the stylo-pharyngeus, it per forates this muscle. In following the course here described, it forms a slight curve, the con vexity of which looks downwards, and it sends off several branches, which are principally dis tributed to the pharynx and isthmus of the fauces. These branches vary very considerably in size and in number in different subjects, but the general distribution of the nerve is in all eases nearly the same. When the branches are few in number, this is compensated for by their increased bulk, and when they are more numerous they are of diminished size. This nerve generally anastornoses with the par vagum within the cranium by a pretty distinct branch.* As the nerve lies within the foramen laecrum it presents two swellings or ganglia upon it, and gives off some small branches. The superior of these two ganglia is considerably smaller than the inferior, and has been termed the ganglion ju gulare by J. Muller, (fig. 225). It is described by AIiillert as generally present, though small, placed upon the posterior or external side of the nerve, and situated at the cranial end of the foramen lacerum. It can only be distinctly seen after the dura mater has been removed, and the upper margin of the opening chiseled away. I have repeatedly observed this gan glion jugulare in the human subject. In one case which I lately dissected, where it was comparatively large, very distinct, and pre sented undoubtedly all the appearance of a true ganglion, it appeared to me, after careful examination, that this swelling does not include the whole of the nerve, but is confined, as Muller states, to the posterior filaments. These posterior filaments do not seem to differ other wise in appearance from the anterior. This ganglion was first pointed out by Ehrenritter, and mentioned by Soemmerring on his audio rity.t Very little attention seems to have been paid to this ganglion, so that when it was lately re-described by Miiller,§ it was supposed that its existence in the human subject had been hitherto unknown.* Mayer, of Bonn, had, previous to this (1833), described two small swellings upon the root of the glosso-pharyn geal in the ox, but he failed to detect any similar ganglion in the human species. No nervous filaments either leave or join that part of the trunk of the nerve upon which the gan glion jugulare is placed. The inferior ganglion (ganglion petrosum, ganglion of Andersch) is considerably larger than the superior, is of an oblong shape, and includes all the filaments of the nerve. It is described by Anderscht as about five lines in length, and commencing about four lines below the place where the nerve perforates the dura mater. No doubt, if we include all that portion of the trunk of the nerve which appears to be somewhat increased in size, it may sometimes measure five lines, but the true gangliform enlargement is consi derably less. As Wutzerj remarks, it is rarely found to exceed two lines in length. This gan glion lies in a distinct depression in the trous portion of the temporal bone, which Andersch terms receptaculum ganglioli petrosi.