The Sense of Smell
In the dog we trace the triumph of
olfactory power
. How indistinct must be that scent which is communicated to, and lingers on, the ground by the momentary contact of the foot of the hare, the fox, or the deer; yet the hound, of various breeds, recognises it for hours, and some sportsmen have said for more than a day. He also can not only distinguish the scent of one species of animal from another, but that of different animals of the same species. The fox-hound, well broken-in, will rarely challenge at the scent of the hare, nor will he be imposed upon when the crafty animal that he pursues has taken refuge in the earth, and thrusts out a new victim before the pack.
The sense of smelling is, to a certain degree, acute in all dogs. It is a provision wisely and kindly made, in order to guide them to their proper food, or to fit them for our service. It may possibly be the medium through which much evil is communicated. Certain particles of a deleterious nature may be, and doubtless are, arrested by the mucous membrane of the nose, and there absorbed, and the constitution, to a considerable degree, becomes affected. Hence appears the necessity for attention to ventilation, and especially to prevent the membrane of the nose from being habitually stimulated and debilitated by the effluvia generated in a close and hot kennel.
M.
instituted some curious experiments on the sense of smelling, and he was led to believe that it depended more on the fifth pair of nerves than on the olfactory nerve. He divided the fifth pair, and from that moment no odour, no puncture, produced the slightest apparent impression on the membrane of the nose. In another dog he destroyed the two olfactory nerves, and placed some strong odours beneath the nostrils of the animal. The dog conducted himself as he would have done in his ordinary state. Hence he concluded it probable that the olfactory nerve was not that of smelling.
The simple fact, however, is, that there are two species of nerves here concerned — those of common and of peculiar sensation. The olfactory nerve is the nerve of smelling, the fifth pair is that of common sensation. They are to a certain degree necessary to each other.
. — This leads us to the consideration of the term "scent." It expresses the odour or effluvium which is constantly issuing from every animal, and especially when that animal is in more than usual exercise. In a state of heat or excitement, the pores of the skin appear relaxed, and a fluid or aqueous vapour is secreted, which escapes in small or large quantities, adheres to the persona or substances on which it falls, and is, particularly, received on the olfactory organs. The hound, at almost the earliest period, begins to comprehend the work which he has to perform. The peculiar scent which his nostrils imbibe urges him eagerly to pursue but the moment he ceases to be conscious of the presence of the effluvium, he is at a perfect loss.
Mr.
, in his work on the
Chase
, very properly observes, that
"the scent most favourable to the hound is when the effluvium, constantly perspired from the game as it runs, is kept by the gravity of the air at the height of his breast. It is then neither above his reach nor does he need to stoop for it. This is what is meant when the scent is said to be breast-high."
When the leaves begin to fall, the scent does not lie well in the cover. It frequently alters materially in the same day. This depends principally on the condition of the ground and the temperature of the air, which should be moist but not wet. When the ground is hard and the air dry, there will seldom be much scent. The scent rarely lies with a north or east wind. A southerly wind without rain is the best. Sudden storms are sure to destroy the scent. A fine sunshiny day is not good; but a warm day without sun is always a good one. If, as the morning advances, the drops begin to hang on the bushes, the scent will not lie. During a white frost the scent lies high, and also when the frost is quite gone; but at the time of its going off the scent never lies. In a hard rain, if the air is mild, the scent will sometimes be very good. A wet night often produces the best chases. In heathy countries, where the game brushes the grass or the boughs as it goes along, the scent seldom fails. It lies best on the richest soils; but the countries that are favourable to horses are not always so to hounds. The morning usually affords the best scent, and the game is then least able to escape. The want of rest, added perhaps to a full belly, gives the hounds a decided superiority over an early-found fox; and the condition of the ground and the temperature of the air are circumstances of much importance.
Such are the results of the best observations on scent; but, after all, we have much to learn concerning it. Many a day that predicated to be a good one for scent has turned out a very bad one, and
vice versa
. An old or experienced sportsman, knowing this, will never presume o make sure of his scent.
We shall be forgiven if we pursue this subject a little at length.
There is not only a constant appropriation of new matter to repair the losses that animals are continually sustaining, but there is a constant elaboration of gaseous or fluid matter maintaining the balance of the different systems, and essential to the continuance of life. This effluvium, as the animal moves from place to place, is attracted and detained for a while by the substances with which it comes into contact, or it remains floating in the atmosphere.
There is a peculiar smell or scent belonging to each individual, either generally or under peculiar circumstances.
The sportsman takes advantage of this; and, as most species of dogs possess great acuteness of olfactory power, they can distinguish, or are readily taught to distinguish, not only the scent of the hare from that of the fox, but that of the hare or fox which they are pursuing from that of half a dozen others that may be started during the chase.
The dogs that are selected for this purpose are those the conformation of whose face and head gives ample room for the development of the olfactory apparatus, and these are the different species of hounds; but a systematic education, and too often a great deal of unnecessary cruelty, is resorted to, in order to make them perfect in their work. The distinction between the scent of the fox and that of the hare is soon learned by the respective packs; and, when it is considered that the hunted hare is perspiring at every pore, and her strength being almost exhausted, she is straining every limb to escape from her pursuers, the increasing quantity of vapour which exudes from her will prevent every other newly started animal from being mistaken for her.
It has been well observed that when the atmosphere is loaded with moisture, and rain is at hand, the gas is speedily dissolved and mingles with the surrounding air. A storm dissipates it at once, while the cessation of the rain is preceded by the return and increased power of scent. A cold, dry easterly wind condenses and absorbs it, and this is even more speedily and irretrievably done by superabundant moisture. On fallows and beaten roads the scent rarely lies well, for there is nothing to detain it, and it is swept away in a moment; while over a luxuriant pasture, or by the hedge-row, or on the coppice, it lingers, clinging to the grass or the bushes. In a sunshiny day the scent is seldom strong; for too much of it is evaporated by the heat. The most favourable period is a soft southerly wind without rain, the scent being of the same temperature and gravity with the atmosphere. Although it spreads over the level, it rises not far above the ground, and, being 'breast high', enables the hound, keeping his muzzle in the midst of it, to run at his greatest speed. The different manners or attitudes in which the dog runs afford pleasing and satisfactory illustrations of the nature of the scent. Sometimes they will be seen galloping with their noses in the air, as if their game had flown away, and, an hour or two afterwards, every one of them will have his muzzle on the ground. The specific gravity of the atmosphere has changed, and the scent has risen of fallen in proportion.
A westerly wind stands next to a southerly one, for a hunting morning. This is all simple enough, and needs not the mystification with which it has been surrounded. A valuable account of this may be found in Johnson's
Shooting Companion
, a work that is justly and highly approved.
Mr.
[a]Delmé]
Radcliffe has also, in his splendid work on "the noble science," some interesting remarks on the scent of hounds. He says that there ia an idiosyncracy, a peculiarity, in their several dispositions. Some young hounds seem to enter on their work instinctively. From their first to their last appearance in the field they do no wrong. Others, equally good, will take no notice of anything; they will not stoop to any scent during the first season, and are still slack at entering even at the second; but are ultimately distinguished at the head of the pack; and such usually last some seasons longer than the more precocious of the same litter.
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