of the tongue. Their division does not affect the motions of that organ or its power of taste; both remain entire. Lastly, when the glossopharyngeal nerve is divided, the sense of taste is lost; whilst, the other nerves being uninjured, motion and tactile sensibility remain. Professor Panizza found, that when the glosso-pharyngeal nerves were divided, the animal could not taste coloquintida.

1

From a series of experiments, however, similar to those of Panizza and Mr. Broughton, Mr. Mayo inferred, in conformity with an opinion previously expressed by him, that the lingual branch of the fifth is the proper nerve of taste, and that it possesses also general sensibility; that the ninth or hypoglossal is the nerve of voluntary motion; whilst the glosso-pharyngeal is in part a nerve of voluntary motion and in part of general sensibility, but not of taste. Again: the experiments and researches of Dr. John Reid, have satisfied him, that after the perfect section of the glosso-pharyngeal nerves on both sides, the sense of taste is sufficiently acute to enable the animal to recognise bitter substances; and his inference is, that this nerve may participate with others in the function of taste; but that it assuredly is not the special nerve of that sense. Prof. J. Müller1 esteems it certain, both from his own experiments and those of M. Magendie and others, as well as from pathological observations, that the lingual branch of the fifth is the principal nerve of taste of the tongue; but he does not regard it proved, that the glosso-pharyngeal has no share in the perception of taste at the posterior part of the tongue, and in the fauces. Dr. Carpenter," from a consideration of how nearly the sense of taste is allied to that of touch, and bearing in mind the distribution of the two nerves, thinks it not difficult to arrive at the conclusion, that both nerves are concerned in the function; and that there seems good reason to believe the glosso-pharyngeal to be exclusively that through which the impressions made by disagreeable substances taken into the mouth are propagated to the medulla oblongata, so as to produce nausea, and excite efforts to vomit; whilst M. Longet' regards the lingual branch of the fifth and the glosso-pharyngeal as necessary for the general and special sensibility of the gustatory organs, "the action of the one perfecting that of the other, both as respects the general sensibility and the gustatory sensibility of the tongue." It may be proper to add, that experiments seem to show, that the glosso-pharyngeal possesses also a direct motor influence. Such is the inference of Messrs. J. Müller, Volkmann, and Hein. The last observer, whose experiments were carefully performed, states that his results accord completely with those of Volkmann. When the roots of the glosso-pharyngeal nerve were irritated in the recently cut-off heads of calves and dogs, after removing the brain and medulla ob1 Anatomical and Physiological Commentaries, p. 2, Lond., 1822.

"Bostock's Physiology, 3d edit., p. 732, Lond., 1836; and Mayo, Outlines of Physiology, 4th edit., p. 314, Lond., 1837.

3 Edinburgh Medical and Surg. Journal, for Jan., 1838, p. 129. See, on this disputed topic, Alcock, in Dublin Journal, for Nov., 1836, and J. Guyot, Archives Générales de Médecine, Janvier, 1837.

4 Elements of Physiology, by Baly, P. v. p. 1321, Lond., 1839.

5 Human Physiology, p. 173, and p. 253, Lond., 1842.

Todd and Bowman, The Physiological Anatomy and Physiology of Man, p. 442, London,

7 Traité de Physiologie, ii. 297, Paris, 1850.

longata, and separating their roots from those of the pneumogastric, contractions always ensued in the stylo-pharyngeus muscle. From all the facts adduced by recent observers, Mr. Paget' thinks it probable,First. That the glosso-pharyngeal is chiefly the nerve of taste, and, in a less degree, a nerve of common sensation; and Secondly. That, according to the experiments of MM. Müller and Hein, it is the motor nerve of the stylo-pharyngeus, and probably also of the palato-glossus. Lastly, M. de Blainville supposes, that the sense of taste is, perhaps, neither sufficiently special nor sufficiently limited in extent to have a separate nervous system; and therefore that all the nerves of the tongue are equally inservient to the sense, as the different nerves of the skin, which proceed from numerous pairs, are equally inservient to touch or tact.2

Such is the existing state of uncertainty regarding this interesting point of physiology: the view of Panizza appears, however, to the author, to be most in accordance with analogy; and in all respects most worthy of adoption. From the experiments and observations of Bellingeri, Montault, Diday, C. Bernard, and Verga,3 it would appear, that the filaments of the chorda tympani, which are united and confounded with those of the lingual branch of the fifth pair, are in an inexplicable manner connected with gustation. When the facial nerve has been paralyzed, or divided above the origin of the tympanic branch, the sense of taste has been impaired. The functions of the chorda tympani are by no means determined;-some esteeming it as a sensory, others as a motor nerve; whilst others, again, believe it to possess both sensory and motor properties.

The immediate function of taste, as has been remarked, is to give the sensation of savours. This function, like touch, is instinctive; requires no education; cannot be supplied by any of the other senses, and is accomplished as soon as the tongue has acquired the necessary degree of development. To this it may be replied, that the very young infant is not readily affected by savours. In all cases, however, certain sapid bodies excite their usual impression; and, in the course of a few months, when the organ becomes developed, the sense acquires a high, and often inconvenient, degree of acuteness.

The mediate or auxiliary offices of gustation are few, and limited in extent. It does not afford much instruction to the mind. The chemist and mineralogist occasionally gain information through it; but it is never considered to merit the rank of an intellectual sense: on the contrary, it is classed with olfaction as a corporeal sense.

To appreciate a savour accurately, the sapid substance must remain for a time in the mouth: when rapidly swallowed, the impression is feeble, and almost null. Of this fact we take advantage when compelled to swallow nauseous substances; whilst we retain a savoury article long in the mouth, in order that we may extract its sweets. How different, too, is the consent of the auxiliary organs under these two circumstances! Whilst a luscious body augments the secretion of the

'Brit, and For. Med. Rev., April, 1845, p. 580. 'Adelon, op. cit., i. 309.

8 Cited by M. Longet, op. cit., p. 365, Paris, 1850.

salivary glands, or causes the "mouth to water," as it has been called -projecting the saliva, at times, to a distance of some feet from the mouth, and disposing every part to approach or mingle with it-a nauseous substance produces constriction of every secretory organ; an effect which extends even to the stomach itself, so that it often rejects the offending article, as soon as it reaches the cavity. We can thus understand how, cæteris paribus, an article, that is pleasing to the palate, may be more digestible than one that excites disgust; and conversely. Of the "consent of parts," exerted between the stomach and the organ of taste, we have a familiar illustration in the fact,-that whatever may be the goût, with which we commence a meal on a favourite article of diet, we find that the relish is blunted as the stomach becomes filled; and hence the Romans were in the habit of leaving the table once or twice during a meal, and, after having unloaded the organ, of returning again to the charge-"vomunt ut edant, edunt ut vomant."

If we place a sapid substance in the mouth, and then close the nostrils, the taste is diminished,—a fact, which has given rise to the generally prevalent and correct opinion, that an intimate relation exists between the smell and taste. They are, however, distinct. Most sapid substances have an odour or "flavour," which is not appreciated when we prevent the air from passing through the nasal fossæ. This renders the impression on the gustatory nerves still less marked, but it exists. Gustation is likewise diminished by the new sensation produced in the nostrils by their closure; so that the same amount of attention is not directed to the sense of taste.

Among animals we see great diversities in this sense. Whilst none possess the refined taste of man; there are many, which are capable, by taste or smell, of knowing plants that are nutritive from those that are noxious to them; and it is unusual for us to find that an animal has died from eating such as are unquestionably poisonous to it. Yet, as we have remarked, a substance, that is noxious to one, may be eaten with impunity by another; and, if we select animals, and place them in a field containing plants, all of which are ranked as poisons, and are poisonous to a majority of them, we find that not only has a selection been made by each animal of that which is innocuous to it, but that the substance has furnished nourishment to it, whilst it might have proved fatal to others. All this must be dependent upon peculiar, and inappreciable organization.

The sense of taste is more under the influence of volition than any other. It is provided with a muscular apparatus, by which it can be closed or opened at pleasure; and, in addition, ordinarily requires the assistance of the upper extremity to convey the sapid substance to the mouth. The sense can, therefore, be exercised either passively or actively; and, by cultivation, it is capable of being largely developed. The spirit taster to extensive commercial establishments exhibits the truth of this in a striking manner. In his vocation, he has not only to taste numerous samples, but to appreciate the age, strength, flavour, and other qualities of each: and the practised individual is rarely wrong in his discrimination. With almost all, if not all, these "tasters," the custom is to take a small quantity of the liquor into the mouth; throw

it rapidly around that cavity, and eject it. A portion, in this way, comes in contact with every part of the membrane; and of course impresses not only the lingual, but the other ramifications of the fifth pair. The gourmet of the French-somewhat more elevated in the scale than our ordinary epicure-prides himself upon his discrimination of the nicest shades of difference and excellence in the materials set before him. Many gourmets profess to be able to pronounce, by sipping a few drops of wine, the country whence it comes, and its age; and, according to Stelluti, can tell, by the taste, whether birds put upon the table are domesticated or wild,-male or female. Dr. Kitchener2 asserts, that many epicures are capable of saying in what precise reach or stretch of the Thames the salmon on the table has been caught, and Sir Astley Cooper was in the habit of relating the remarkable case of a professional friend, who could discriminate by the taste the beef furnished by a particular London butcher.3

This acuteness of sense is by no means desirable. Doomed to meet, in his progress through life, with such a preponderance of what demands. obtuseness rather than acuteness of feeling, the epicure must be liable to continual annoyances and discomforts, which the less favoured can never experience.

In disease, gustation often becomes greatly depraved; and the various morbid tastes have been accounted for by depraved secretions in the mouth, acting as foreign sapid substances on the papillæ. Certain tastes, however, cannot be explained in this way, and must be regarded as nervous phenomena. If the epithelium be covered with a fur, taste may be lost or impaired, and be instantaneously restored as soon as the coating is removed. M. Magendie observed, that dogs, after the injection of milk into their veins, licked their lips, and gave other evidences of tasting. When Dr. E. Hale, in an experiment referred to in another part of this work, injected castor oil into one of his veins, he distinctly tasted the oil a short time afterwards. Messrs. Todd and Bowman suggest that such phenomena, if uniformly present, might be occasioned by the transudation of the fluid from the vessels to the nerves of the papillæ; and this may be the true explanation, although it is not easy to see that such transudation could occur in the case of castor oil.

SENSE OF SMELL OR OLFACTION.

The object of this sense is to appreciate the odorous properties of bodies. It differs from the last in the circumstance that the body does not come into immediate contact. It is only necessary that an odorous emanation from it shall impinge upon the organ of sense. Still, it does not essentially vary in its physiology from the sense of taste.

1. ANATOMY OF THE ORGAN OF SMELL.

The organ of smell is a mucous membrane, which lines the nasal cavities, and is called Schneiderian or pituitary. It resembles that which covers the organ of taste, except that the nervous papillæ are more delicate, to correspond with the greater tenuity of the body that 'American Quarterly Review, ii. 427. 2 Cook's Oracle, 3d edit., p. 229, Lond., 1821. 3 Life of Sir Astley Cooper, Bart., by Bransby Blake Cooper, Esq., F. R. S., ii. 137, Lond., 1843. The Physiological Anatomy and Physiology of Man, p. 448, Lond., 1845.

Vertical Section of the Middle Part of the Nasal Fossæ, giving a Posterior View of the Arrangement of the Ethmoidal Cells, &c.

1. Anterior fosse of the cranium. 2. The same covered by the dura mater. 3. Dura mater

turned up. 4. Crista galli of the ethmoid bone.

5. Its cribriform plate. 6. Its nasal lamella.

has to make the impression. The membrane lines the whole of the bony cavities called nasal fossæ, which are constantly open anteriorly and posteriorly, to permit the air that traverses them to proceed to the lungs. The anterior aperture is covered by a kind of pent-house or capital, for the purpose of collecting the odorous particles. This capital is called the nose. The essential part of the organ is the pituitary or olfactory membrane,-the other parts being superadded to perfect the

sense.

The bony portions of the nose are separated from each other by the vomer. This bony septum is prolonged, by means of cartilage, to 7. Middle spongy bones. 8. Ethmoidal cells. the anterior extremity of the nose, 9. Os planum. 10. Inferior spongy bones. 11. so that the nasal fossæ are divided Vomer. 12. Superior maxillary bone. 13. Its union with the ethmoid. 14. Anterior parietes into like parts, which have no commuof the antrum Highmorianum, covered by its membrane. 15. Its fibrous layer. 16. Its mucous nication with each other, but open membrane. 17. Palatine process of the superior together, posteriorly, into the top ered by the mucous membrane. 19. Section of of the pharynx. Within each of the nares are two convoluted or turbinated bones-generally called ossa spongiosa vel turbinata; and, by the French, cornets. These are situate one above the other; the superior formed of a plate of the ethmoid bone-the inferior a distinct bone. They divide the general cavity of each nostril into three passages or meatus. The inferior meatus is broad and long; the least oblique, and least tortuous; the middle is narrow, almost as long, but more extensive from above to below; and the superior is much shorter, more oblique, and still narrower. The narrowness of these passages in the living subject is so great, that the slightest tumefaction of the membrane renders the passage of air through the fossæ extremely difficult. This is the cause of the difficulty of breathing through the nose, that attends "a cold in the head." Into the two upper passages, cavities in certain bones open, which considerably enlarge the extent of the fossæ. These are called sinuses; and are the maxillary, palatine, frontal, sphenoidal, ethmoidal,-the last being sometimes termed ethmoidal cells.

All the cavities are lined by the delicate pituitary membrane, or by a prolongation of it. In the nasal fossæ it augments the thickness of the turbinated bones. It resembles the mucous membranes in general in its composition; and adheres firmly to the bones and cartilages, which it covers. Its aspect is velvety, owing to a multitude of minute papillæ; and it receives a great number of vessels and nerves. The sinuses are lined by a prolongation apparently of the same membrane, differing, however, in some respects from the other. The whole of the