wanting in the infant, which, notwithstanding, appreciates odours;that they exist only in the mammalia;—and that experiments would seem to show, that the upper part of the olfactory organ is more particularly destined for the function, and that the sinuses, which, as well as the membrane covering the middle and lower spongy bones, are supplied by filaments from the fifth pair of nerves, are not sensible to odours.

Messrs. Todd and Bowman'-from the fact, that on the septum narium and turbinated bones bounding the direct passage from the nostrils to the throat, the lining membrane is rendered thick and spongy by the presence of ample and capacious submucous plexuses of both arteries and veins, of which the latter are by far the larger and more tortuoussurmise, and Dr. Carpenter' thinks, with much probability, that the chief use of these may be to impart warmth to the air, before it enters the proper olfactive portion of the cavity; as well as to afford a copious supply of moisture, which may be exhaled by the abundant glandulæ seated in the membrane. "The remarkable complexity of the lower turbinated bones in animals with active scent, without any ascertained distribution of the olfactory nerves upon them, has"-they remark-"given countenance to the supposition, that the fifth pair may possess some olfactory endowment, and seems not to have been explained by those who rejected that idea. If considered as accessory to the perfection of the sense in the way above alluded to, this striking arrangement will be found consistent with the view, which thus limits the power of smell to the first pair of nerves." That the upper part of the nasal fosse is the great seat of smell is proved by the facts referred to regarding the uses of the nose. Dessault mentions the case of a young female, who had a fistula in the frontal sinuses, and who could not perceive an odorous substance, when presented at the orifice of the fistula, because there was no communication with the proper portion of the nasal fossæ, although she was capable of breathing through the opening. M. Deschamps, the younger, relates the case of a man, who had a fistula of the frontal sinus, through which ether might be injected without its odour being appreciated, provided all communication had been previously cut off between the sinus and the upper part of the nasal fossæ; but if this precaution had not been taken, the sense was more vivid, when the odours passed through the fistulous opening, than when they reached the organ by the ordinary channel. Again;-M. Richerand3 found that highly odoriferous injections, thrown through a fistulous opening in the maxillary sinus or antrum of Highmore, produced no olfactory sensation whatever.

All these facts would seem to lead to the belief, that the upper part of the nasal fossæ, on which the first pair or olfactory nerves are distributed, is the chief seat of olfaction, and that the inferior portions of these fossæ, as well as the different sinuses communicating with them, are not primarily concerned in the function: but, doubtless, offer secondary advantages of no little importance. This conclusion, would, however, seem to admit, what is not by any means universally admitted, that the

'Physiological Anatomy and Physiology of Man, ii. 3.

2 Art. Smell, Cyclop. of Anat. and Physiol., Pt. xxxvi. p. 694, Lond., June, 1849. 3 Elémens de Physiologie, édit. 13ème par Bérard, p. 202, Bruxelles, 1837.

olfactory is the sole or chief nerve of smell. Especially difficult is it to embrace this view, and not to believe that the spongy bones and sinuses, on which the fifth pair are distributed, are agents in perfecting the sense, when we find them so largely developed in animals that possess unusual delicacy of smell, as the dog and elephant. It has already been remarked, that the ancients believed the olfactory nerves to be canals for conveying away the pituita or phlegm from the brain. Diemerbroeck, also, maintained this view. At the early part of the last century, however, the olfactory was supposed to be the proper nerve of smell, and the opinion prevailed, with few dissentient voices, until within the last few years. Inspection of the origin and distribution of the nerve seems to indicate it as admirably adapted for special sensibility connected with smell. It is largely developed in animals in proportion to their acuteness of the sense, and is distributed on the very part of the pituitary membrane to which it is necessary to direct air, loaded with odorous emanations, in order that they may be appreciated. M. Magendie' has, however, endeavoured to show by experiment, that the sense of smell is in no wise, or little, dependent upon the olfactory nerve, but upon branches of the fifth pair. Prior to the institution of his experiments, he had observed with astonishment, that after he had removed the cerebral hemispheres, with the olfactory nerves of animals, they still preserved this sense. He had noticed, too, that it continued in lunatics, who had fallen into a state of stupor, and in whom the substance of the brain appeared, on dissection, greatly disorganized. These facts induced him to expose the olfactory nerves on living animals, and to experiment upon them; and he found, in the first place, that the nerves were insensible to puncture, pressure, and the contact of the most odorous substances. He afterwards satisfied himself, that after their division the pituitary membrane not only preserved its general sensibility, appreciated the contact of bodies, but also, strong odours, those of ammonia, acetic acid, oil of lavender, Dippel's oil, &c. On the other hand, having divided the fifth pair of nerves within the cranium, and left the olfactory nerves entire, he remarked, that the pituitary membrane had lost its general sensibility; was no longer sensible to contact of any kind; and had lost the power of appreciating odours. From these experiments, he considered himself justified in inferring, that the olfactory nerve does not preside over the general sensibility of the nose; that it has, at the most, a special sensibility as concerns odours; and that if the olfactory be the nerve of smell, it requires the influence of the fifth pair, in order that it may act. Lastly; he asks, may not the general and special sensibility be comprised in the same nerve in the sense of smell, as they are in that of taste;-in the fifth pair?

These experiments are interesting; but they by no means establish, that the fifth pair is the olfactory nerve. The numerous facts, already mentioned, attract us irresistibly to the first pair or olfactory, as they have been exclusively called. It has been already remarked, that the fifth is concerned in all the facial senses; that it conveys to them general

Anatome Corporis Humani, lib. iii. cap. 8, Ultraject., 1672. "Précis Elémentaire, 2de édit., i. 132.

sensibility or feeling; and that some of them are unquestionably supplied with nerves of special sensibility;-the eye with the optic; and the ear with the auditory; but that neither the one nor the other can exert its special function, without the integrity of the fifth. The olfactory nerve is probably in this category,—is the nerve of special sensibility. It is true, that in the experiments of M. Magendie the animal appeared to be affected by odorous substances, after the division of the first pair; but a source of fallacy existed here, in discriminating accurately between the general and special sensibility. Some of the substances employed were better adapted for eliciting the former than the latter;-ammonia and acetic acid, for example.

The immediate function of the sense of smell is to appreciate odours. In this it cannot be supplied by any other sense. The function is instinctive; requires no education; and is exerted as soon as the parts have attained the necessary degree of development. In many respects the sense is intimately connected with that of taste; and the impressions made upon each are frequently confounded. In the nutritive function, the smell serves as a kind of advanced guard or sentinel to the taste; and warns us of the disagreeable or agreeable nature of the aliment; but if a substance repugnant to the smell be agreeable to the taste, the smell soon loses its aversion, or at least becomes less disagreeably impressed. The smell is not, however, in man so useful as a sentinel to the taste, as it is to animals: there are many bodies,-those containing prussic acid for example,-which are extremely pleasing by the odours they exhale, and yet are noxious to man. In the animal kingdom, this sense is greatly depended upon, and is rarely a fallacious guide. It enables animals to make the proper selection of the noxious from the innocent;-the alimentary from that which is devoid of nutriment; the agreeable from the disagreeable; and the power appears to be instinctive or dependent upon inappreciable varieties of structure in the organs concerned in olfaction.

As an intellectual sense, smell is not entitled to a higher rank than taste. Its mediate functions are very limited. It enables the chemist, mineralogist, and perfumer, to discriminate bodies from each other. We can, likewise, by it form a slight-but only a slight-idea regarding the distance and direction of bodies, owing to the greater intensity of odours near an odorous body, than at a distance from it. Under ordinary circumstances, the information of this kind derived by olfac tion is inconsiderable; but in the blind; and in the savage, who is accustomed to exercise all his external senses more than the civilized, its sphere of utility and accuracy is largely augmented. Of this we shall have to speak presently. We find it, too, surprisingly developed in certain animals; in which it is considered, by the eloquent Buffon, as an eye that sees objects not only where they are, but where they have been, as an organ of gustation, by which the animal tastes not only what it can touch and seize, but even what is remote, and cannot be attained; and he esteems it a universal organ of sensation, by which animals are most readily and most frequently impressed; by which they act and determine, and recognise whatever is in accordance with, or in

opposition to, their nature. The hound amongst quadrupeds affords us a familiar example of the extreme delicacy of this sense. For hours after the passage of game, it is capable of detecting its traces; and the bloodhound can be trained to indicate the human footsteps with unerring certainty.

Until of late years, it was almost universally believed, that many of the birds of prey possess an astonishingly acute sense of smell. Humboldt' relates, that in Peru, Quito, and in the province of Popayan, when they are desirous of taking the gigantic condor- Vultur gryphus of Linnæus-they kill a cow, or horse, and in a short time, the odour of the dead animal attracts those birds in numbers, and in places where they were scarcely known to exist. It is asserted, too, that vultures went from Asia to the field of battle at Pharsalia, a distance of several hundred miles, attracted thither by the smell of the killed! Pliny,3 however, exceeds almost all his contemporaries in his assertions on this matter. He affirms, that the vulture and the raven have the sense of smell so delicate, that they can foretell the death of a man three days beforehand, and in order not to lose their prey they arrive upon the spot the night before his dissolution! The turkey-buzzard of the United States is a bird of this class, and it is surprising to see how soon they collect from immense distances after an animal has died in the forests. The observations and experiments of the ornithologist Audubon would seem, however, to show that this bird possesses the sense of smell in a less degree than the carnivorous quadruped. He stuffed the skin of a deer with hay, and after the whole had become perfectly dry and hard, placed it in an open field on its back, and in the attitude of a dead animal. In the course of a few minutes a vulture was observed flying towards it, which alighted near, and began to attack it; tearing open the seams, and pulling out the hay; but finding that it could obtain nothing congenial to its taste, it took flight. It was found, too, that when animals in an advanced state of putridity were lightly covered over so as to prevent vultures from seeing them, they remained undisturbed and undiscovered, although the birds repeatedly flew over them. In some other experiments it was found, that birds of prey were attracted by well-executed representations of dead animals painted on canvass and exposed in the fields,-and in others, that young vultures, enclosed in a cage, exhibited no tokens of their perceiving food, when it could not be seen by them, however near them it was brought. These results-which were obtained, also, by Dr. Bachman in the presence of a number of scientific gentlemen of Charleston, South Carolina-are strange, inasmuch as the olfactory apparatus of the turkey-buzzard, when examined by the comparative anatomist, exhibits great development, and admirable adaptation for acuteness of smell. They are confirmed, however, by more recent experiments on the condor by Mr. Charles Darwin,' a distinguished natu

'Rec. de Zoolog. et d'Anat. Comp., 2de livr., p. 73. Paris, 1807. "Haller, edit. cit., tom. v. lib. xiv. p. 158. 3 Hist. Nat., lib. x. cap. 6, p. 230, Lugd. 1587. Ornithological Biography, p. 33, Boston, 1835; Loudon's Mag. of Nat. Hist., vii. 167. 5 Journal of Researches into the Natural History and Geography of the countries visited during the voyage of H. M. S. Beagle round the World. Amer. edit., New York, 1846.

ralist. He tied several condors by ropes in a long row at the bottom of a wall; and having folded up a piece of meat in white paper, he walked backwards and forwards carrying it in his hand at the distance of about three yards from them; but no notice whatever was taken of it. He then threw it on the ground within one yard of an old male bird, which looked at it for a moment with attention, but regarded it no more. With a stick he pushed it closer and closer, until at last the bird touched it with its beak: the paper was then instantly torn off . with fury, and at the same moment every condor in the long row began struggling, and flapping its wings. "Under the same circumstances, it would have been quite impossible to have deceived a dog."

As the organ of smell, in all animals that respire air, is situate at the entrance of the organs of respiration, it is probable that its seat, in insects, is in the mouth of the air tubes. This sense appears to guide them to the proper kinds of food, and to the execution of most of the few offices they perform during their transient existence. Occasionally, however, they are deceived by the resemblance between odours of substances very different in other qualities. Certain plants, for example, emit a cadaverous odour similar to putrid flesh, by which the flesh-fly is attracted, and led to deposit its ova in places that can furnish no food to its future progeny.

As regards the extent of the organ of smell, man is undoubtedly worse situate than most animals; and all things being, in other respects, equal, it may be fair to presume, that those, in which the olfactory membrane is most extensive, possess the sense of smell most acutely. It is curious, however, that certain animals, which have the sense of smell in the highest degree, feed on the most fetid substances. The dog, for instance, riots in putridity; and the birds of prey, to which reference has been made, but whose acuteness of smell, we have seen, has been contested, have similar enjoyment. The turkey-buzzard is so fetid and loathsome, that his captors are glad to loosen him from bondage; and it is affirmed, that if his ordinary fœtor be insufficient to produce his release, he affords an irresistible incentive, by ejecting the putrid contents of his stomach upon them!1

One inference may, perhaps, be drawn from this penchant of animals with exquisite olfactories for putrid substances;-that the taste of the epicure for game, kept until it has attained the requisite fumet, is not so unnatural as might at first sight appear.

Like the senses already described, that of smell is to a certain extent under the influence of volition:-in other words, it can be exerted actively, and passively. Its active exercise-as when we smell any substance to enjoy its sweets, or test its odorous qualities generally requires prehension, the proper direction of the head towards the object, and more or less contraction of certain muscles of the alæ nasi. Doubtless, here again, the papillæ are capable of being erected under attention, as in the senses of taste and touch. On the other hand, we can throw obstacles in the way of the reception of disagreeable odours; and, if necessary, prevent their ingress altogether, by compressing the nostrils with the upper extremity.

1 Wilson's American Ornithology, by Geo. Ord, Philad., 1803-1814.