ORGAN OF SMELLLTNG.
The nose is a cavity of very irregular figure, formed chiefly by the banes of the face, and communicating with the various sinuses or bony cells formed in the head.
It is separated by the brain above by the cribriform lamella of the ethmoid bone. This separation is a perfect one, and the two cavities of the cranium and nose are wholly distinct from each other, although they are supposed, by the unin formed in anatomy, to communicate to gether.
The bottom of the cavity is formed by the upper surface of the pallet.
The general cavity is divided into two equal halves, called nostrils, by the sep tum narium, a thin and flat bony parti tion, descending from the cribriform la mella to the palate. The flat surface of the septum may therefore be said to form the inner side of the nostril ; and its outer side presents three bony eminences, call ed the concha swim, or turbinated hones.
Moreover, the following excavations or sinuses open into the cavity at various parts. Two frontal sinuses ; numerous cells of the ethinoid bone ; two sphenoi dal sinuses ; and two great hollows iv, the upper jaw-bone, called the antra, or max illary sinuses.
The front openings of the nostrils are well known. This aperture is heart-sha ped in the skeleton, the broadest part be ing towards the mouth ; but it is much al tered in the recent subject by the apposi tion of pieces of cartilage, the broadest of which are the lateral portions, termed aim nasi. Behind, the nostrils open by large apertures into the upper and anterior part 'of the pharynx, above the velum pendu lum palati.
The sides of the bony cavity just de scribed are covered by a thick, soft, and very vascular membrane, called mem brana schneideriana, or pituitaria. Its surface is constantly moistened by a se. cretion of mucus from the arteries, with which it is very copiously supplied. This prevents the effects which the current of air in respiration would otherwise pro duce, of drying the membrane. It is only an increased quantity of this secretion, altered too somewhat in its quality, that is discharged from the nose in colds, and which is popularly supposed to come from the brain. This membrane extends into the cells which communicate with the nose, but is thinner and less vascular there.
The cthmoidal cells open into the cavi ty of the nose, partly above, and partly under, the loose edge of the superior tur binated bone. The frontal sinuses open into the front of these cells ; and the sphenoidal sinuses into the hack part of them. The antrummaxillare has a round opening between the two turbinated bones. The nasal duct opens under the inferior of these bones : and the expand ed orifice of the eustachian tube is just at the communication between the back of the noise and the pharynx.
The filaments of the olfactory nerves, having penetrated the cribriform are distributed to the pituitary membrane that covers the septum nasi and superior turbinated bone.
Several small branches from the fifth pair are also distributed on the nose, at different parts.