THE BONES. 61 



it presents, for. zygnmutic. anter., which is the end of the Canal, zygom. 

 anter., for the n. subcutaneous malsB; a groove leading to for. zygomat. poster., 

 the commencement of the Canal, zygnrnat poster. 



c. Posterior, temporal surface, hollowed out for muse, temporalis, presents 

 the end of the canal, zygomat. poster., namely, the for. zygomat. poster, for the 

 n. zygomaticus s. temporalis. 



2. Processes: 



a. Pr. frontalis, the superior, unites with the Frontal, and behind with the 

 Sphenoid bone. 



b. Pr. temporalis, unites with the process of the temporal bone to form the 

 zygomatic arch arcus zygomaticus, for the muse, masseter. 



c. Pr. maxillaris, triangular, broad, and little projecting, unites with the Pr. 

 zygomat. of the upper jaw. 



Formation. The malar bone consists almost entirely of com- 

 pact bony tissue ; spongy tissue is only found at the anterior 

 inferior border. 



Development begins early from one central point about the 

 50th day of foetal life. At birth the orbital margin is sharp, and 

 it is not rounded until later. 



62. 3. Ossa Nasalia, Nasal bones, 2 



Situation : next to one another, sometimes united, beneath the 

 frontal, between the two nasal processes of the sup. maxillary 

 bones ; oblique from above and behind, to below and before. 



Shape : a long quadrangle, above, narrow and thick, below, 

 broad and thin. 



Conjunctions: with Frontal, Superior Maxillary, Ethmoid 

 bones and Nasal cartilages. 



1. External, cutaneous surface, covered by the muse, pyramidalis nasi, flat, 

 somewhat convex, with a large, and several smaller foramina for the Vasa 

 nutritia. 



2. Internal surface, the anterior portion of the nasal cavity, presents grooves 

 for vessels and nerves, the nerv. Ethmoidalis. 



3. Borders, a. Superior, fitting into the incisura nasalis of the Frontal 

 bone. 



b. Inferior, supporting the lateral cartilages of the nose, between them a 

 foramen for a nerve filament and arterial twig, nerv. Ethmoidalis. 



c. Internal, forms with the bone of the other side the crista nasalis, for the 

 lamina perpendicularis of the Ethmoid, and above for the spina nasalis, of the 

 Frontal bone. 



d. External, longer than the last described, unites with the nasal process of 

 the upper jaw bone. 



Development : from one osseous centre, commencing at the end 

 of the 2d month of foetal life. The nasal bones are completely 

 formed at birth, but not the cartilages. 



