The London medical dictionary: including, under distinct heads, every branch of medicine, viz. anatomy, physiology, and pathology, the practice of physic and surgery, therapeutics, and materia medica ; with whatever relates to medicine in natural philosophy, chemistry, and natural history (Volume 2).

  • Parr, Bartholomew, 1750-1810.
Date:
1819
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Licence: Public Domain Mark

Credit: The London medical dictionary: including, under distinct heads, every branch of medicine, viz. anatomy, physiology, and pathology, the practice of physic and surgery, therapeutics, and materia medica ; with whatever relates to medicine in natural philosophy, chemistry, and natural history (Volume 2). Source: Wellcome Collection.

Provider: This material has been provided by the National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)

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    size a common thread. They arise from the base of the testes, and running half round the root of the crura me- dullae oblongatae, adhere, by a membrane, to the ante- rior lateral part of the processus annularis, pass through the foramina lacera, and are spent on themusculi troch- leares, the superior oblique muscles of the eye. They are called fiathetici from their rolling the eye with vio- lence or fury. The origin of the trochleares is, however, various, and they seem to have a more intimate connec- tion with the brain than any other nerves; yet no part of their office shows such a connection, or appears im- portant. The Jifth pair, trigemini, arise from the annular process, where the medullary processes of the cerebel- lum are joined to the tuber. This nerve seems to arise in two portions: the anterior is small, and somewhat elevated above the other; the posterior originates a little lower. These portions are connected by a cellular mem- brane in which a little artery often creeps. In fact, though in a few individuals connected with the cerebrum, this is truly a nerve of the cerebellum. It enters the dura mater, near the point of the petrous process of the tem- poral bone, and sinking close by the receptacula at the sides of the sella turcica, each becomes thicker, forms a distinct ganglion, and passes from the skull in three great branches; one to the orbit of the eye and forehead, through the foramen lacerum ; one to the upper jaw and face through the foramen rotundum; and another to the lower jaw and tongue, through the foramen ovale. The Jirst^ the ophthalmic,, before it passes through the foramen lacerum, sends off a branch to the inter- costal, and forms the first connection between the two systems. It is then distributed to the glands, fat, membranes, and muscles of the eye, with a twig to the forehead, sending a considerable branch through the in- ternal anterior orbitar hole to the brain, in order to join the olfactory nerve. These very extensive connections explain various morbid phcenomena, as the watering of the eyes, from a stimulus to the nerves of the nostrils, the effect of sneezing from a strong light, and stopping the same convulsion, by a pressure on the internal can- thus, or indeed why sneezing itself, a convulsive action of the muscles of respiration, is occasioned by a stimu- lus to the nostrils. The second branch, maxillaris sufierior, passes put at t-he foramen rotundum of the sphenoidal bone, and gives nerves to the palate, sphenoidal sinus, and nostrils, supplies the antrum maxillare, and the upper teeth. It comes out at the external orbitar foramen, previously sending a branch through the substance of the os max- illare, which comes out at Stenos duct, to be distribut- ed on the fore part of the palate. The remainder, which passes through, is lost on the orbicular muscle of the eyelids, the nose and upper lip, where it seems to unite with some branches of the seventh pair. The third, maxillaris inferior, goes out at the foramen ovale of the sphenoidal bone, and supplies all the muscles of the lower jaw, and those between it and the OS hyoides. It sends a branch to the tongue, where it meets the ninth pair, and from the root of this last branch the chorda tympani is reflected, or rather the chorda is added to the lingual nerve. It then supplies the salivary glands, the tonsils, the external ear, where it joins a branch of the portis dura of the seventh pair, the teeth of the lower jaw, and from thence the chin and under lip. From these connections, convulsions of the lower jaw arc attended with salivation, angina, with a pain of the ear and teeth, and the senses of smelling and tasting are probably related. If true, that com- pressing the nostrils will destroy the sensation of the palate, the reason will be sufficiently evident from this description, and we shall equally see why the toothach produces convulsions, as well as why cauteries to the external ear, or blisters behind it, sometimes relieve pains of the teeth. The sixth fiair, the abducentes, the smallest, except the fourth, arise from the fore part of the corpora pyramidalia; and, in their passage below the dura mater, where they are contiguous to the carotid, appear to send off a reflected branch, and when joined with some from the ophthalmic branch of the fifth pair, to form the original of the intercostal. The sixth pairj somewhat enlarged, now pass through the foramina lacera to be lost on the abductor muscle of the eye. A dispute has been maintained with obstinacy whether the sixth pair sends or receives this branch from the sympathetic; but anatomists have not decided the fact, and the knife probably cannot decide. The eye, of all the external organs, is, however, the only one whose motions are sometimes involuntary, and the intercostal system is exclusively destined to those muscles which are not under the influence of the will. It is singular that this circumstance, though so obvious, and useful in determining the controversy, should not have occurred; but the distinction is in a great measure new. We may add, at this place, that the third, fourth, fifth, and sixth pair of nerves, pass a considerable way under the dura mater, along the sides of the sella turcica, surrounded with a reticular plexus of vessels, and very near the large trunks of the internal carotid, before they pass through the foramina of the cranium. The seventh pair, the auditory, appear to come from the side of the root of the annular process, behind the conjunction of the medullary processes of the cere- bellum with the tuber, accompanier' '-]' an artery of an unusual size, and entering <he iueatus auditorius, divides into two branches, the/zor^zo mollis and the/ior- tio dura. These two branches, however, on a minute examination, seem to have two distinct origins, the portio dura from the crus cerebelli, and the4)ortio mol- lis from the striae in the fourth ventricle. Prochaska indeed observes, that he has not been always able to trace their origin so far as these striae ; and, though many former anatomists of credit have supported this source, he thinks the striae in the fourth ventricle by no means essential to the auditory nerve. The portio mol- lis soon loses its firm coats, and from this circumstance it is denominated. It enters the petrous bone, and in this softer state is disseminated on the internal ear. The other, supported by its harder coats, passes through Fallopius' aquaeduct, in its passage by the side of the tym- panum, where a nerve, sent to the lingual branch of the inferior maxillary nerve, along the outside of the Eusta- chian tube, and across the cavity of the tympanum (chorda tympani), is joined to it. The portio dura comes from the encephalon between the styloid and mastoid processes of the temporal bone, giving branches to the smaller muscles, and then passing through the parotid gland, supplies the muscles of the face, neck, and cranium, including the external ear. Its branches having thus a connection with the three branches of the fifth, and, as we shall see, of the second cervical, occa- sion numerous instances of sympathy, obvious to every one who reflects on their distribution.