152 SPECIAL ANATOMY OF THE SKELETON 



the whole or only a portion of the hard palate, and usually involves the soft palate also. The 

 cleft is in the middle line, except it involves the alveolus in front, when it follows the suture 

 between the main portion of the bone and the premaxillary bone. Sometimes the cleft runs 

 on either side of the premaxillary bone, so that this bone is quite isolated from the maxillary 

 bones and hangs from the end of the vomer. In such a case the premaxillary bone usually 

 contains the germs of the central incisors only. In some cases there is no premaxillary bone 

 and the great gap in the lip is in the median line. Cleft palate (page 106) is usually associated 

 with harelip, which, when single, is almost always on one side, corresponding to the position 

 of the suture between the lateral incisor and canine tooth. Some few cases of median harelip 

 have been described. In double harelip there is a cleft on each side of the middle line. 



The outlines and the height of the arch of the palate vary greatly in different persons. A 

 narrow palate with a high arch is common in idiots and certain degenerates. 



The bones of the face are sometimes fractured as the result of direct violence. The two 

 most commonly broken are the nasal bone and the mandible, and of these, the latter is by far the 

 most frequently fractured of all the bones of the face. Fracture of the nasal bone is for the most 

 part transverse, and takes place about half an inch from the free margin. The broken portion 

 may be displaced backward or more generally to one side by the force which produced the lesion, 

 as there are no muscles here which can cause displacement. The malar bone is probably never 

 broken alone; that is to say, unconnected with a fracture of the other bones of the face. The 

 zygomatic arch is occasionally fractured, and when this occurs from direct violence, as is usually 

 the case, the fragments may be displaced inward. This lesion is often attended with great diffi- 

 culty or even inability to open and shut the mouth, and this has bee'n 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 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 mandible 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 frac- 

 tures 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 maxilla and mandible are both of them frequently the seat of necrosis, though the disease 

 affects the latter much more frequently than the former. It may be the result of periostitis, 

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

 by mercury; it not infrequently 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 the 

 manufacture of matches. 



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 imper- 

 fectly developed teeth, the "dentigerous cyst." Solid innocent tumors include the fibroma, 

 the chondroma, and the osteoma. Of malignant tumors there are the endotheliomata, the 

 sarcomata, and the epitheliomata. The sarcomata are of various kinds, the spindle-celled, 

 the round-celled, which are of a very malignant character, and the myeloid sarcomata, prin- 

 cipally 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 origi- 

 nating in the antrum or nasal fossae. 



Both mandible and maxilla occasionally require excision for tumors and in some other condi- 

 tions. The maxilla is removed by an incision from the inner canthus of the eye, along the side 

 of the nose, around the ala, and down the middle line of the upper lip. A second incision is 

 carried outward from the inner canthus of the line 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, and the central incisor of the diseased side is removed. The connections 

 of the bone to the other bones of the face are then divided with a narrow saw and bone-cutting 

 forceps. They are (1 ) the junction with the malar bone, passing into the sphenomaxillary fissure; 

 (2) the nasal process; a small portion of its upper extremity, connected with the nasal bone in 

 front, the lacrimal 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-jaw 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 



