BONES OF THE FACE 355 



frontal bones unite to form the anterior part of the cranial cavity and 

 the upper walls of the orbits, leaving a space between them for the reception 

 of the ffthmoid bone. The tico jiarietals are situated at the upper and 

 lateral parts of the brain-case, and are of an irregularly quadrilateral figure 

 — each meeting its fellow in the median line on the top of the head. The 

 temporal hone overlaps the parietal on each side, with its squamous portion, 

 while the petrous part runs in towards its fellow on the opposite side, con- 

 stituting a part of the floor of the brain-case, and separating that cavity 

 into two. It contains within its bony structure the true organ of hearing. 

 The occipital hone occupies the bick part of the cranium, and makes up the base. 

 It has a large opening (the foramsn magnum), for the passage of the medulla 

 oblongata, and vertebral arteries ; and on each side of this are large smooth 

 articulating surfaces, for the attachment of the atlas vertebra. The sphenoid 

 hone is of a most remarkable shape, resembling slightly a bat, with its wings 

 partially expanded. The body and wings complete the middle of the base 

 of the skull, and the legs go to form part of the walls of the nasal cavity 

 and mouth. Lastly, the cethmoid bme is made up of a cribriform plate sup- 

 porting the anterior lobes of the briin, and giving passage to the olfactory 

 nerves, which spread over the cellu'ar structure that constitutes the whole 

 substance of this bone. Another thin plate contributes to form the inner 

 and posterior wall of the orbits. 



BONES OF THE FACE 



The face is made up of the nasal, posterior, and anterior maxillarj', 

 molar, lachrymal, and palate bones, the four turbinated bones, vomer, and 

 lower jaw. 



Fia. 3. — Longitudinal Section of Head. 



1, 2, 3. The upper walls of the cranium. 10. Petrous portion of temporal bone. 



4. Frontal sinus. 11. Vomer. 



5. Nasal bones. 12. Inferior turbinated bone. 



6. Superior turbinated bone. 13. Palatine plate of posterior maxillary. 



7. ^Ethmoidal cells. 14. Posterior maxillary bone, outer wall. 



8. Sphenoid bone, uniting with 15. Anterior maxillary' bone. 



9. Occipital bone. 



The nasal hones are long and thin, forming the roof of the nostrils. 

 Posteriorly they are broad, and taper gradually forwards to a sharp point. 

 The postei'ior maxillary hones are triangular in shape, thick behind, and 

 presenting thin edges in front. The anterior maxillary hones are of an 

 irregular shape, being connected with the corresponding edges of the 

 posterior maxillary and nasal bones, and completing with the former the 

 roof of the mouth. The malar hone has an irregularly triangular shape, 



