OLFACTORY SYSTEM. In anatomy, the olfactory sys tem consists of the nose and the nasal cavities which support the olfactory mucous membrane for the perception of smell in their upper parts, and act as respiratory passages below.
The bony framework of the nose is part of the skull (q.v.), but the outer nose is only supported by bone above ; lower down its shape is kept by cartilaginous plates. The expanded lower part of the side of the nose, the "ala," is only formed of skin, both externally and internally, with fibro-fatty tissue between the layers. The nasal cavities are separated by a septum covered in its lower two-thirds by thick, highly vascular mucous membrane composed of columnar ciliated epithelium with masses of acinous glands embedded in it, while in its upper part it is covered by the less vascular but more specialized olfactory membrane. Near the front of the lower part of the septum a slight opening into a short blind tube, which runs upward and backward, may some ucts which boil at 110-113° C and 178-181° C respectively.
Diolefines.—The most important of the diolefines, are those containing the two double linkings separated by one single linking (conjugated double linkings). :3-Butadiene (Erythrene), the simplest member of this type, is an easily liquefiable gas (b.p. —5° C) formed by chlori nating n-butyl chloride and passing the product over heated soda lime (W. H. Perkin, junr., J. Soc. Chem. Ind., 1912).
(G. T. M.) times be found; this is the vestigial remnant of "Jacobson's organ." The supporting framework of the septum is made up of ethmoid above, vomer below, and the "septal cartilage" in front. The outer wall of each nasal cavity is divided into three meatus by the overhanging turbinated bones (see fig. 2). Above the superior turbinated is a space between it and the roof known as the "recessus spheno-ethmoidalis," into the back of which the "sphenoidal air sinus" opens. Between the superior and middle turbinated bones is the "superior meatus," containing the open ings of the "posterior ethmoidal air cells," while between the middle and inferior turbinateds is the "middle meatus," which is the largest of the three and contains a rounded elevation known as the "bulla ethmoidalis." Above and behind this is often an
opening for the "middle ethmoidal cells," while below and in front a deep sickle-shaped gutter runs, the "hiatus semilunaris," which communicates above with the "frontal air sinus" and below with the opening into the "antrum of Highmore" or "maxillary an trum." The "inferior meatus" is below the inferior turbinated bone, and, when that is lifted up, the valvular opening of the nasal duct (see EYE) is seen. The roof of the nose is narrow, and here the olfactory nerves pass in through the cribriform plate. The floor is wider so that a coronal section through each nasal cavity has roughly the appearance of a right-angled triangle.