226 THE SKELETON. 



direct violence, as is usually the case, the fragments may be displaced inward. This lesion is 

 often attended with great difficulty or even inability to open and shut the mouth, and this has 

 been stated to be due to the depressed fragments perforating the temporal muscle, but would 

 appear rather to be caused by the injury done to the bony origin of the Masseter muscle. 

 Fractures of the superior maxilla may vary much in degree, from the chipping off' of a portion 

 of the alveolar arch, a frequent accident when the "old key" instrument was used for the 

 extraction of teeth, to an extensive comminution of the whole bone from severe violence, as the 

 kick of a horse. The most common situation for a fracture of the inferior maxillary bone is in 

 the neighborhood of the canine tooth, as at this spot the jaw is weakened by the deep socket for 

 the fang of this tooth ; it is next most frequently fractured at the angle ; then at the symphysis, 

 and finally the neck of the condyle or the coronoid process may be broken. Occasionally a 

 double fracture may occur, one in either half of the bone. The fractures are usually compound, 

 from laceration of the mucous membrane covering the gums. The displacement is mainly the 

 result of the same violence as produced the injury, but may be further increased by the action 

 of the muscles passing from the neighborhood of the symphysis to the hyoid bone. 



The superior and inferior maxillary bones are both of them frequently the seat of necrosis, 

 though the disease affects the lower much more frequently than the upper jaw, probably on 

 account of the greater supply of blood to the latter. It may be the result of periostitis, from 

 tooth irritation, injury, or the action of some specific poison, as syphilis, or from salivation by 

 mercury; it not unfrequently occurs in children after attacks of the exanthematous fevers, and 

 a special form occurs from the action of the fumes of phosphorus in persons engaged in match- 

 making. 



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 chondroma, 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-forceps, 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 now 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 or 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 occasionally requires tapping for suppuration. This may be done through the 

 socket of a tooth, preferably the first molar, the fansrs of which are most intimately connected 

 with the antrum, or through the facial aspect of the bone above the alveolar process. This latter 

 method does not perhaps afford such efficient drainage, but there is less chance of 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. 



