Fig. 256.—Defective development of Mandible from fixation of jaw due to tuberculous osteomyelitis in infancy.

Treatment.—When the cause of the fixation is in the joint itself, the best treatment is to resect one or both condyles.

When the fixation is due to cicatricial contraction of the soft parts, mobility is best restored by forming an artificial joint well in front of the cicatricial tissue, as suggested by Esmarch.

CHAPTER XXII
THE TONGUE

Surgical Anatomy.—The tongue is composed of interlaced, striped muscle fibres, partly consisting of the terminations of the extrinsic muscles, and partly of the intrinsic muscles. A median fibrous septum divides it into two lateral halves so completely that but little communication takes place between the blood vessels and lymphatics of the two sides. It is covered by stratified squamous epithelium. For practical purposes it is described as consisting of an anterior or oral part, and a posterior or pharyngeal part.

The oral part, which includes the anterior two-thirds of the organ, is mobile, and the epithelium on its dorsal aspect is modified so as to form several varieties of papillæ. A slight median depression is recognisable on the dorsum as far back as the vallate (circumvallate) papillæ, which mark the boundary between the oral and pharyngeal parts. A double fold of mucous membrane—the frenum—connects the under aspect of the tip with the floor of the mouth and the mandible. On each side of the frenum, under the mucous membrane of the tip, are mucous glands—apical glands—in which cysts sometimes form. On the lateral border of the tongue, just in front of the anterior palatine arch, are several vertical folds of mucous membrane—the folia linguæ, or foliate papillæ.

The pharyngeal part, or base of the tongue, forms the anterior wall of the pharynx, and is attached to the hyoid bone. Its mucous membrane is devoid of papillæ, but contains numerous lymphoid follicles—the lingual tonsil. The foramen cæcum lies just behind the apex of the vallate papillæ in the middle line.

The chief artery, the lingual, a branch of the external carotid, passes forward beneath the hyoglossus muscle, and is continued to the apex as the ranine, lying nearer the under than the upper aspect of the tongue. The pharyngeal part is supplied by the dorsalis linguæ branch. The blood is returned to the internal jugular by the ranine vein, which can be seen under the mucous membrane on the inferior aspect near the frenum, and by the venæ comites of the lingual artery and its branches.

The hypoglossal is the motor nerve of the tongue. The lingual branch of the mandibular (inferior maxillary) supplies the anterior two-thirds with common sensation. It is accompanied by the chorda tympani branch of the facial, which probably carries the taste fibres. The glosso-pharyngeal supplies the posterior third of the tongue with both common and gustatory sensation.