The two _inferior turbinated bones_ lie along the outer walls of the nasal fossæ. They are thin scroll-like bones covered with mucous membrane and serve to heat the air as it passes in. Sometimes when one has a cold, the membrane and the bone too swell up and close the nares. Loss of the sense of smell in a bad cold may be due to such swelling and the consequent impeding of the entrance of odoriferous particles--a condition that would likewise interfere with the sense of taste. Part of the bone is sometimes removed, to enlarge the passage, enough being left to warm the air. Lastly, there is the _inferior maxillary bone_ or _lower jaw_. This has a horseshoe-shaped body and two _rami_, one at either end. Each ramus has a pointed process in front called the _coronoid process_, into which is inserted the temporal muscle. At the back, and separated from the coronoid process by the sigmoid notch, is the _condyle_, which articulates with the glenoid fossa on the temporal bone. The rami also give attachment to the masseter muscle at its point of insertion. In adult age the ramus is almost vertical but in old age the portion of the jaw hollowed out into alveoli for the teeth becomes absorbed and the angle of the jaw becomes very obtuse. On the inner side of the jaw near the middle on either side is the fossa for the _sublingual gland_, while the _submaxillary gland_ lies in a fossa farther back on either side. Sometimes the lower jaw is dislocated and when once this has occurred it is liable to occur again, the ligaments becoming stretched. CHAPTER IV. THE ORGANS OF SPECIAL SENSE. =The Nose.=--The nose, the organ of the sense of smell, is composed of a framework of bones and cartilages, the bridge being formed by the two nasal bones, and the septum by the vomer and the triangular cartilage. It consists of two parts, the _external nose_ and the internal or _nasal fossæ_, which open to the face by the anterior nares or nostrils and into the pharynx by the posterior nares. Externally it is covered with skin, internally with ciliated mucous membrane. The _fossæ_ have the inferior turbinated bones along their outer walls and are divided into three parts known as the _superior_, the _middle_, and the _inferior meatus_, the middle one connecting with the antrum of Highmore, while into the inferior meatus the lachrymal canal empties. There are many small muscles of which little use is made, although in forced respiration, as in pneumonia, where every aid to breathing is called into play, even the alæ nasi or nostrils are made to exert what muscular power they possess in order to supply more air. [Illustration: FIG. 18.--The nasal cavity. (After Sobotta.)]