Tedical and Physical Journal. 3 OF VOL. XLIX.] JUNE, 1823. [NO. 292. * many fortunate discoveries in medicine, and for the detection of numerous errors, the world is ndebted to the rapid circulation of Monthly Journals; and there never existed any work, to which the Faculty, in Europe and America, were under deeper obligations, than to the Medical and Physical Journal of London, now forming a long, but an invaluable, series.-RUSH. ORIGINAL COMMUNICATIONS, ART. I.-Second Part of a Paper on the Nervous System. N compliance with your request, and that of other friends, I hall now endeavour to fulfil my promise of giving a slight ketch of the Superadded Nerves. But, as a considerable time has elapsed since the publication of my last communication to your Journal, I shall, before entering upon the subject again, make a short recapitulation of the characteristic distinctions of the Regular, or Original, Nerves. Under this class were comprised the fifth, or trigeminus, the suboccipital, the seven cervical, the twelve dorsal, the five lumbar, and the five sacral; in all, thirty-one pairs of nerves.* To all of these nerves the following characters are common : -an origin by two distinct sets of filaments; a ganglion on one of the roots; a distribution, in a lateral direction, to the different parts of the body. We find, moreover, that they are all compound nerves; being the media through which the voluntary motions common to all animals are ordered, and through which the sense of touch and common sensibility are bestowed on the different parts. When the trunk of one of these nerves is divided, not only are the muscles to which it goes, deprived of the power of executing certain motions, but the sensibility of the part is entirely destroyed; but, if only the set of filaments by which the nerve arises from the anterior column of the spinal marrow be cut, the voluntary power over the muscles alone is lost: whereas, if the posterior set of filaments be divided, the sensibility of the part is destroyed, while the voluntary power continues unimpaired.† * See the Plate in the Number of this Journal for December 1822, and C, C, C, in the accompanying plan. It is now quite unnecessary to state any circumstances to prove, that the sole merit of the discovery of the distinctions between the characters and functions of NO. 292. 3 N . 'It may be also stated, that the facts furuished by the examination of the structure of the spinal marrow, and the results of experiments, have induced Mr. BELL to believe that the different fibres or striæ of nervous matter, minister to the same order of functions through all their length. For example, if we trace the nervous cord of that part of the crus cerebri which gives origin to the third nerve, or motor oculi, down to the cauda equina, we shall find that, through its whole course, it is connected with nerves of the same function or character. We may trace from it the third, the sixth, the ninth, and the anterior roots of the spinal nerves; and nearly all those nerves can be proved to regulate the voluntary powers. After having arranged the nerves just described under one class, we shall find the intricacy of the nervous system much diminished; and, in attempting to unravel it farther, we shall arrive at the following important conclusion,-that all the other nerves (with the exception of the sympathetic,) have relation to parts which may be considered as superadded to the original frame of the body; and that their branches and connections are numerous or complicated, in proportion to the variety of functions which the superadded organs perform. I shall not now enter upon the description of the nerves of sense, or of those which are distributed to the parts within the orbit, although all of them may be considered as superadded nerves, but confine my observations to those exhibited in the accompanying plan; which, it will be acknowledged, are the nerves that, by their distribution and connexions, mainly contribute to the intricacy of the system. These nerves will be found to be chiefly intended for the purpose of regulating the functions of such parts as are more or less connected with respiration. They are the portio dura of the Seventh; the three divisions of the Eighth,-viz. the glosso pharyngeal, the par vagum, and the spinal accessory; the Ninth, or lingualis; the phrenic, and the external respiratory. I shall give a short description of each of these nerves; and, by references to comparative anatomy, endeavour to show upon what circumstances their existence and their complication depend. First, of the PORTIO DURA of the SEVENTH, or respiratory nerve of the face, marked in the Plan 7, and seen passing forward from the ear upon the muscles of the eye, nose, and mouth. the roots of the spinal nerves, is due to Mr. Bell; for it is not only now publicly acknowledged in this country, but has also been fully admitted by M. Majendie, to whom the merit had erroneously been given by some gentlemen. See my communication in the Number for October. The nerves of the orbit are very complicated; but their intricacy has been, in a great measure, unravelled by the description given of them in two papers which have this season been presented to the Royal Society by Mr. Bell Although this be very generally called the Facial Nerve, it is not found upon the face unless there be some consent of motions established between the muscles of the face and the respiratory organs. Thus, in fishes, the nerve, instead of being distributed on the face, passes to the muscles of the gills; and, in the gamecock, we find it passing principally to the muscles below the jaw, and to those which raise the feathers of the neck. Although the nerve be generally described as rising along with the auditory nerve, yet we find in many animals that it rises with the branches of the eighth: this is particularly observable in fishes and in birds.* The proportion of the portio dura, or facial respiratory nerve, to the fifth pair, is greater in man than in any other animal. In the monkey, its proportion to the fifth is diminished; but still in this animal it is more complicated than in the dog, or any of the carnivorous animals, the intricacy of the branches being apparently in proportion to the number of the muscles of expression. From the lion, the dog, and the cat, we may descend to the horse, ass, and cow in the latter animals, there is a marked difference in the distribution of the nerve, from that of either the monkey or the dog; for, excepting a few branches, which pass to the muscles of the external ear and to the eyelid, the whole of the respiratory nerve is confined to the muscles of the nostrils and side of the mouth. There are, however, some varieties in the classes of the graminivorous animals. In the gazelle, sheep, and deer, the distribution of the nerve is still more simple than in the horse; while in the camel it is more profuse, and is, in this respect, intermediate between that of the carnivorous and the graminivorous animals. Indeed, the expression of the enraged camel is sufficiently ferocious; and the manner in which he shows his tusks, when dying, is very similar to that of a carnivorous creature. Although we are told by those who have seen an elephant in a rage, that he is most sublime and terrific, still the anatomy of the portio dura of this animal leads me to suspect that the expression of rage, however terrible, must be quite different from that of the ferocious snarl of the lion. In the face, it must be in a great measure confined to the contortions of the proboscis, and to the eye; for, except a few branches to the eyelids, the distribution of this nerve of In the Leçons d'Anatomie Comparée, à description is given of the origin and course of this nerve in the calf. The connexions between it and the par vagum under the ear, though the same, as in other mammaliæ, are there described as the origins of the facial nerve. Since the names portio dura and facial nerve are used indiscriminately in this country, it is probably in consequence of this description that some gentlemen have described the portio dura in the calf as rising with the par vagum. |