148 OSTEOLOGY. 



the greater palatine artery and anterior palatine nerve. Towards its upper and 

 posterior part the nasal surface of the body displays the irregular, more or less 

 triangular, opening of the maxillary sinus. This aperture which, in the articulated 

 skull opens into the middle meatus of the nose, is much reduced in size by articula- 

 tion with the lacrimal, ethmoid, palate, and inferior conchal bones. In front of 

 the lacrimal groove the nasal surface is ridged horizontally by the crista conchalis 

 (inferior conchal crest), to which the inferior conchal bone is attached. Below this 

 the bone forms the lateral wall of the inferior nasal meatus, receiving the termina- 

 tion of the lacrimal groove. Above, and for some little distance also on the 

 medial side of the frontal process, it constitutes the smooth lateral wall of the 

 atrium of the middle meatus. 



Processes. The processus zygoma ticus (zygomatic process), which is 

 placed on the antero-lateral surface of the body, is confluent anteriorly with 

 the facial surface of the body; posteriorly, where it is concave from side to 

 side, with the infra-temporal surface; whilst superiorly, where it is rough and 

 articular, it forms the apex of the triangular orbital surface, and supports the 

 zygomatic bone. Inferiorly, its anterior and posterior surfaces meet to form an 

 arched border, which fuses with the alveolar process opposite the root of the first 

 molar tooth, and serves to separate the anterior from the infra-temporal surfaces of 

 the body. 



The processus frontalis (frontal process) arises from the upper and anterior 

 part of the body. It has two surfaces one lateral, the other medial. The lateral is 

 divided into two by a vertical ridge (crista lacrimalis anterior), which is the upward 

 extension of the infra-orbital margin. The narrow strip of bone behind this ridge 

 is hollowed out, and leads into the lacrimal groove below. Posteriorly the edge 

 of the frontal process here articulates with the lacrimal, and so forms the fossa for 

 the lodgment of the lacrimal sac (fossa sacci lacrimalis). In front of the vertical 

 crest, to which the medial palpebral ligament is attached, the lateral surface is 

 confluent below with the facial surface of the body, and forms the side of the root of 

 the nose. Here may often be seen a vascular groove entering the bone. Its anterior 

 edge is rough, or grooved, for articulation with the nasal bone. Superiorly the 

 summit of the process is serrated for articulation with the nasal notch of the 

 frontal bone. The medial surface of the frontal process is directed towards the 

 nasal cavity. It is crossed obliquely from below upwards and backwards by a ridge 

 the agger nasi or ethmoidal crest which is considered to be a vestige of the naso- 

 turbinal which is met with in some mammals. Below this the bone is smooth and 

 forms the upper part of the atrium of the middle meatus, whilst the ridge 

 itself articulates posteriorly with the anterior part of the middle conchal bone, 

 formed by the inferior concha of the ethmoid bone. 



The processus alveolaris (alveolar process) projects from the inferior surface 

 of the body of the bone below the level of the palatal process. Of curved form, it 

 completes, with its fellow of the opposite side, the alveolar arch, in which are 

 embedded, in sockets or alveoli, the roots of the teeth of the maxilla ; ordinarily 

 in the adult, when dentition is complete, each alveolar process supports eight teeth. 

 Piercing the medial surface of the alveolar border behind the incisor teeth two 

 small vascular foramina are usually visible. When any or all the teeth are shed 

 the alveoli become absorbed, and the process may under these circumstances be 

 reduced to the level of the plane of the palatine process. Posteriorly the alveolar 

 process ends below the maxillary tuberosity of the body ; anteriorly it shares in the 

 formation of the intermaxillary suture. 



The processus palatinus (palatine process), of the form of a quadrant, lies in 

 the horizontal plane; it has two surfaces superior and inferior and three borders, 

 a straight medial, a more or less straight posterior, and a curved lateral, by which 

 latter it is attached to the medial side of the body and alveolar process as far back 

 as the interval between the second and third molar teeth. Its inferior surface, 

 together with that of its fellow, forms the anterior three-fourths of the vaulted 

 hard palate ; it is rough and pitted for the glands of the mucous membrane of the 

 roof of the mouth, and is grooved, near the alveolar margin, by one or two 

 channels which pass forward from the pterygo - palatine canal and transmit the 



