or rather carrying forward a tubular prolongation of that membrane, they reach the side of a depression in the base of the skull, which has been likened to a Turkish saddle, where the anterior swells out into a large knot or ganglion, named after its discoverer the Gasserian ganglion; after which it divides into three divisions; the first passing into the orbit, from its connection with the eye termed opthalmic; the second, from its distribution being principally to the upper jaw, is called the superior maxillary ; and the third sent to the lower jaw is named inferior maxillary. The anterior root joins the third branch alone, so that the two first are composed of filaments solely from the anterior root, while the third is truly a compound nerve like those which proceed from the spinal We shall consider the three divisions of the

marrow.

fifth separately.

Opthalmic Branch.-This enters the orbit at the same passage with the third, fourth, and sixth, when it immediately divides into branches; one proceeds forwards, and is reflected on the forehead, where it establishes connections with the frontal plexus of the facial; another reenters the skull, and accompanies the first pair of nerves to the nose; a third passes to the lachrymal gland. A small twig runs along the optic nerve, to join others from the third pair. Before they combine, a small ganglion is formed on this twig, termed from its form lenticular; from these arise minute nerves, which pierce the coats of the eye, to be ramified upon its interior. The mucous membrane and other secreting organs are supplied from the opthalmic branch, so that extensive connections are established by it.

Superior Maxillary Branch. This passes through a hole a little posterior to the first, and immediately begins to divide into branches, some of which have ganglions formed in their course. The principal branches are sent to the back part of the nostrils, the pendulous curtain and almonds of the throat, where it forms connexions with the

eighth; to the palate, gums, and teeth of the upper jaw, and externally to the cheek, upper lip, and nose, where it is intimately associated with the facial. A small twig re-enters the skull, passing by the side of the carotid canal: it sends filaments to unite with the sixth and great sympathetic. It then enters a canal, and for a short space be

comes associated with the trunk of the facial, from which it derives some minute filaments, after which it runs through the drum of the ear, and again emerging from the skull, joins the branch of the fifth, which is distributed upon the tongue, and finally it is expended in the neighbourhood of the submaxillary gland.

Inferior Maxillary Branch, formed of a combination of the sensiferous and motiferous filaments of the fifth. The latter are distributed to the muscles which shut the jaw, and also on those which regulate the posterior orifices of the nostrils; the former are ramified upon the tongue, salivary glands, gums, and teeth of the lower jaw, on the external ear, cheek, chin, and lower lip, maintaining communications with the facial, the eighth and ninth, and with the great sympathetic.

The engraving is here introduced to shew the distribution of the facial and fifth nerves on the face, and in order to give an idea of the manner in which nerves are ramified. d is the trunk of the facial, its branches radiating from this situation to the forehead, across the face to the chin, down by the side of the neck; they are seen to communicate with each other, and to join twigs of the three branches of the fifth; a is the frontal branch of the fifth; the facial of the same, and c its submaxillary branch; e are ramifications of the cervical and accessory nerve, forming communications with the facial.

The fifth being profusely distributed upon the integuments of the face, has been unequivocally demonstrated to be the nerve by which feeling is transmitted. From exposure probably to the vicissitudes of external temperature, it is liable to an exquisitely painful affection, named tic douloureux, which is sometimes removed by cutting the nerve affected, the patient preferring the loss of sensibility to the agonizing pain which accompanies the disease. In the cat, the hare, and other animals with large whiskers, the filaments of this nerve have been traced to the bulbs of the hairs, accounting for the delicate tact which these animals are endowed with, and by means of which they are enabled to wind their way in the dark through intricate passages with the greatest facility.

It deserves attention, that the fifth is associated with the organs of the senses of smell, sight, and hearing;

that it exercises that of touch, especially on the lips and tip of the tongue, and that it is the immediate instrument of taste. From the general outline we have given of its distribution, it will be seen that both the first and second branches contribute filaments to the nose, those from the first accompanying the olfactory nerve. Magendie has attempted to prove that these twigs constitute the proper seat of smell, and that the first nerve has nothing to do with that function, though he has seen reason somewhat to modify his opinion. In this he has furnished a notable instance how torturing animals, by what are called experiments, is as apt to mislead and bewilder as elicit truth. It is a source of no small pleasure to know that the conclusions which Sir Charles Bell has arrived at, and the truths which he has succeeded in establishing, were not the result of cruelties committed on our fellowcreatures in the first instance, and that when it became necessary to put them to the test upon living animals, the experiments were previously well devised, and conducted with every consideration of humanity the case would admit of; and in no instance does he have recourse to unnecessary repetitions, furnishing a beautiful contrast to that butcher-like indifference to animal suffering which is so fashionable in the present day, and which is often practised with so little appearance of design, aim, or purpose, that it looks as if it sprung more from the gratification of a depraved and cruel disposition than from the desire for the advancement of science.

Magendie cut the first pair of nerves in dogs, and applied ammonia to the nostrils, when there appeared as much sensibility as ever. He cut the nasal branches of the fifth pair, and the animal no longer displayed evidence of being affected, and therefore he inferred that the fifth was the true nerve of smell. Now, in the first place, ammonia has no odour; it is a powerful stimulant, but does not communicate to us any impression such as the olfactory nerves convey; as a powerful stimulant it is

calculated to rouse the common sensibility of the nostrils, which depends upon the fifth. The other pungent stimulants he employed with the view of upsetting long established opinions, namely, the oils of lavender, of turpentine, and so forth, not only impress the first pair with their odour, but likewise rouse the sensitiveness of the fifth. Then as to the fifth pair being necessary to the exercise of the sense of smell, without having recourse to mangling animals, there was little or no ground to doubt that the destruction of the fifth pair would be attended with derangement of the sense of smell, since the organ by which it was exercised had lost its integrity.

From the distribution of the first branch of the fifth pair upon the iris, the lachrymal organs, and nose, we have an explanation of the connexion which subsists between these parts, affording an example of sympathy, not of that kind which calls forth motion, but sensation; yet although there appears to be a sufficient number of facts to establish the existence of sympathy of sensation, some contend for its being limited to the respiratory system of nerves, and account for the connexions which are displayed between such parts as those on which the first branch of the fifth pair is ramified to the communications with the pathetic and facial. But however that may be, it is well known that pungent substances applied to the nose produce a copious flow of tears; the iris will also be found to contract, and when the curtains are opened in the morning, and a sudden glare of light is thrown upon the eyes, sneezing is apt to follow from the transference of excitement to the nose; and from the connexion which the branches of the fifth establish with the respiratory nerves, the muscles of respiration are powerfully thrown into action, and the air is forcibly expelled through the nostrils. The gratification from snuff-taking does not arise from its odour, but from the stimulus of the sensiferous. nerves. When a hearty pinch is taken, the eyes water, the excitement extends to the forehead, the teeth tingle,