122 THE SKELETON. 



Tumors attack the jaw-bones not infrequently, and these may be either innocent or malig- 

 nant: in the upper jaw cysts may occur in the antrum, constituting the so-called dropsy of the 

 antrum ; or, again, cysts may form in either jaw in connection with the teeth : either cysts con- 

 nected with the roots of fully-developed teeth, the "dental cyst; " or cysts connected with 

 imperfectly developed teeth, the ' ' dentigerous cyst. ' ' Solid innocent tumors include the fibroma, 

 the chondrorna, and the osteoma. Of malignant tumors there are two classes, the sarcomata 

 and the epithelioma. The sarcoma are of various kinds, the spindle-celled and round-celled, of 

 a very malignant character, and the myeloid sarcoma, principally affecting the alveolar margin of 

 the bone. Of the epitheliomata we find the squamous variety spreading to the bone from the 

 palate or gum, and the cylindrical epithelioma originating in the .antrum or nasal fossae. 



Both superior and inferior maxillary bones occasionally require removal for tumors and in 

 some other conditions. The upper jaw is removed by an incision from the inner canthus of the 

 eye, along the side of the nose, round the ala, and down the middle line of the upper lip. A 

 second incision is carried outward from the inner canthus of the eye along the lower margin of 

 the orbit as far as the prominence of the malar bone. The flap thus formed is reflected outward 

 and the surface of the bone exposed. The connections of the bone to the other bones of the 

 face are then divided with a narrow saw. They are (1) the junction with the malar bone, pass- 

 ing into the spheno-maxillary fissure ; (2) the nasal process; a small portion of its upper 

 extremity, connected with the nasal bone in front, the lachrymal bone behind, and the frontal 

 bone above, being left; (3) the connection with the bone on the opposite side and the palate in 

 the roof of the mouth. The bone is now firmly grasped with lion-forc'eps, and by means of a 

 rocking movement upward and downward the remaining attachments of the orbital plate with 

 the ethmoid, and the back of the bone with the palate, broken through. The soft palate is first 

 separated from the hard with a scalpel, and is not removed. Occasionally in removing the upper 

 jaw it will be found that the orbital plate can be spared, and this should always be done if possi- 

 ble. A horizontal saw-cut is to be made just below the infraorbital foramen and the bone cut 

 through with a chisel and mallet. Removal of one-half of the lower jaw is sometimes required. 

 If possible, the section of the bone should be made to one side of the symphysis, so as to save 

 the genial tubercles and the origin of the genio-hyo-glossus muscle, as otherwise the tongue tends 

 to fall backward and may produce suffocation. Having extracted the central or preferably the 

 lateral incisor tooth, a vertical incision is made down to the bone, commencing at the free margin 

 of the lip, and carried to the lower border of the bone ; it is then carried along its lower border 

 to the angle and up the posterior margin of the ramus to a level with the lobule of the ear. 

 The flap thus formed is raised by separating all the structures attached to the outer surface of 

 the bone. The jaw is now sawn through at the point where the tooth has been extracted, and 

 the knife passed along the inner side of the jaw, separating the structures attached to this sur- 

 face. The jaw is then grasped by the surgeon and strongly depressed, so as to bring down 

 the coronoid process and enable the operator to sever the tendon of the temporal muscle. 

 The jaw can be now further depressed, care being taken not to evert it nor rotate it outward, 

 which would endanger the internal maxillary artery, and the external pterygoid torn through 

 or divided. The capsular ligament is now opened in front and the lateral ligaments divided, 

 and^the jaw removed with a few final touches of the knife. 



The antrum of Highmore occasionally requires tapping for suppuration. This may be done 

 through the socket of a tooth, preferably the first molar, the fangs of which are most inti- 

 mately connected with the antrum, or through the facial aspect of the bone above the alveolar 

 process. 1 his latter method does not perhaps afford such efficient drainage, but there is less 

 chance ot food finding its way into the cavity. The operation may be performed by incising 

 the mucous membrane above the second molar tooth, and driving a trocar or any sharp-pointed 

 instrument into the cavity. 



THE HYOID BONE. 



The Hyoid bone is named from its resemblance to the Greek upsilon; it is also 

 called the lingual bone, because it supports the tongue and gives attachment to its 

 numerous muscles. It is a bony arch, shaped like a horseshoe, and consisting of 

 five segments, a body, two greater cornua, and two lesser cornua. It is suspended 

 from the tip of the styloid processes of the temporal bone by ligamentous bands, 

 the stylo-hyoid ligaments. 



The Body (basi-hijal) forms the central part of the bone, and is of a quadri- 

 lateral form; its anterior surface (Fig. 78), convex, directed forward and upward, 

 is divided into two parts by a vertical ridge which descends along the median line, 

 and is crossed at right angles by a horizontal ridge, so that this surface is divided 

 into tour spaces or depressions. At the point of meeting of these two lines is a 

 prominent elevation, the tubercle. The portion above the horizontal ridrr e is 

 directed upward, and is sometimes described as the superior border. The anterior 

 surface gives attachment to the Genio-hyoid in the greater part of its extent 

 above, to the Gemo-hyo-glossus;. below, to the Mylo-hyoid, Styly-hyoid, and 



