THE NOSE: ORGAN OF SMELL
The nose is composed partly of bone and partly of cartilage, the cartilages being firmly attached to the bones and to one another by fibrous tissue.
The bridge consists of the two nasal bones which are projections of the frontal bone of the forehead. From these are continued the nasal cartilages which form one-half to two-thirds of the external nose.
The interior is a large and complicated chamber divided into the right and left nares, or nostrils, by the partition called the septum. This, like the external part, consists of cartilage in front, attached to bone at the back.
The Nostrils, opening on the face in front, run backward for about two inches and open into the pharynx behind. But the single canal is divided into three separate passages some distance inward. This division is effected by the turbinated bones which jut out into the nostril and thus form the upper, middle, and lower air-channels. In this way the warm surface with which cold inhaled air comes in contact is greatly enlarged.
From the mouth cavity the nose is separated by the hard palate. On the external nose, scattered near the tip, are numerous hairs, sebaceous glands, and sweat glands. These glands are very liable to get blocked, giving rise to inflamed spots, and when hairs are pulled out small abscesses are apt to form.
Membrane.—The whole of the interior surface is lined with mucous membrane, and as this has a large area, and is very well supplied with blood, it raises the temperature of inspired air. The mucous membrane of the nose is continuous with that of the pharynx. Any inflammation, such as that which constitutes a “cold in the head,” is therefore extremely liable to extend backward and finally reach the bronchial tubes and lungs.
Over this membrane spread a multitude of small threads or nerves resembling the twigs of a branch; there are many such branches within the nostril, and they join together so as to form larger branches, which may be compared to the boughs of a tree. These finally terminate in a number of stems, or trunks, several for each nostril, which pass upward through apertures provided for them in the roof of the arched cavity, and terminate in the brain.
We have thus, as it were, a leafless nerve-tree whose roots are in the brain, and whose boughs, branches, and twigs spread over the lining membrane of the nostril. This nerve is termed the Olfactory.