Birds and All Nature, Vol. 5, No. 2, February 1899 / Illustrated by Color Photography

by Various

The sense of smell is one that tires most readily. After smelling certain odors for awhile one loses temporarily the power to notice them at all. The sense does not tire as a whole, but it merely becomes inoperative with respect to the odor continually present. Almost any perfume held to the nose soon loses its charm, and is only effective again after a temporary absence. But while one perfume is not sensed a new one presented to the nostrils is eagerly appreciated, showing the sense to be fatigued only with regard to what has been there for some time. The owner of a large rendering establishment in a city was called upon by a committee of citizens who objected to the smells arising from his plant. He went out with the committee to inspect the premises and declared with evident honesty that he could detect nothing disagreeable in the air nor any sort of a scent that did not properly belong to a rendering establishment. Those who work where there are strong and disagreeable odors soon become so accustomed to peculiar smells that they do not notice them at all, although they are keen to detect any unusual odor, as when the liquor in a tanner's vat has not in it the proper admixture of materials.

All the lower animals seem to be positive as to the direction of the source of any scent, but man is powerless in the matter. He merely knows an odor is present, but is unable to tell without moving about whether it comes from one side of him or another. A blindfolded boy cannot tell which side of his nose is nearest to a suspended orange.

To affect this sense a substance must be dissolved or scattered through the atmosphere to be breathed. Whether such substances are divided and used up in giving out odors is still a question. Some of them, as the essential oils, waste away when exposed to the air, but a grain of musk remains a grain of musk with undiminished power after years of exposure. The experiment is such a delicate one in connection with the musk that it has never been settled to the satisfaction of science.

Substances which scatter themselves readily through the air are usually odorous, while those which do not are generally without smell. But many of these when transformed into vapors, as by the application of heat, become strongly odorous. Bodies existing naturally in the gaseous state are usually the most penetrating and effective as odors. Sulphuretted and carburetted hydrogen are examples of these.

College boys sometimes procure from the chemical laboratories of their institutions materials which are used with telling effect on the social functions of higher or lower classes; in one instance a banquet was cleared of guests by the conscienceless introduction of chemicals just before the festivities were to have begun. Efforts to introduce powerful gases as weapons in war have failed because the effect is not confined to the enemy.

Gases which are offensive are not always positively harmful, but as a rule those which offend the nose are to be avoided. Some deadly gases do not affect the sense of smell at all, as in the case of earth damp which stupefies and kills men in mines and wells without warning. But the nose is a great detector of bad air, especially that of a noxious character, and sewer gas as well as other poisonous airs which bring on the worst types of fever are offensive to one who is not living all the time within their range.

But a small part of the mucous membrane of the nose is the seat of this important sense. The olfactory cells are not as easily examined and traced in their connections as are the end organs of the sense of taste. Yet the anatomist finds in the structure of the noses of the flesh-eating animals sufficient indications of their superiority over man in the exercise of the sense of smell. The peculiar development of the membrane and the complicated structure of the nasal cavities in the region occupied by the cells which are supposed to connect with the extreme divisions of the olfactory nerve are all that one would expect from the differences in endowment.

Aside from peculiar powers of smell there are other endowments of noses which are remarkable. The common hog has a snout that is easily moved and has great strength. He can take down a rail fence with it quite as skillfully as a boy would do it. He can turn a furrow in the soil in search of eatable roots, and when the ground is frozen to a considerable degree of hardness he pursues his occupation with unabated zeal and no evident embarrassment.

The fresh-water sturgeon has a large gristle in his nose which boys sometimes convert into a substitute for a rubber ball. His nose is a useful instrument in securing food from the mud in the river bottom. The rhinoceros has a fierce horny protuberance rising from his nose which is valuable to him in war. Indeed some are equipped with two horns, one behind the other. The female rhinoceros with one horn guides her calf with it, causing him to move ahead of her, but the female of the kind with two horns does not use them upon her offspring at all except in anger, and her calf is content to follow her in feeding.

On the coast of California is a large seal called the sea elephant which is notable because the adult male has a proboscis fifteen inches in length when in ordinary temper, but under excitement it is noticed to extend itself considerably beyond its ordinary length. The shrew, the tapir, and the horse also possess something of a proboscis which is useful in feeding.