BONES OF THE FACE. 315 
squamous portion, while the petrous part runs in towards its fellow on the 
opposite side, constituting a part of the floor of the brain case, and sepa- 
rating that cavity into two. It contains within its bony structure the true 
organ of hearing. The occipital bone occupies the back part of the cranium, 
and makes up the base. It has a large opening (the foramen 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 bone is of a most remarkable shape, re- 
sembling 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 ethmoid bone 
is made up of a cribriform plate supporting the anterior lobes of the brain, 
and giving passage to the olfactory nerves, which spread over the cellular 
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 maxillary, 
molar, lachrymal, and palate bones, the four turbinated bones, vomer, 
and lower jaw. 
Fic. 3.—LoNGITUDINAL SECTION oF Heap. 
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. Aithmoidal cells. 14. Posterior maxillary bone, outer wall 
8. Sphenoid bone, uniting with : 15. Anterior maxillary bone. 
9. Occipital bone. 
The nasal bones are long and thin, forming the roof of the nostrils. 
Posteriorly they are broad, and taper gradually forwards to a sharp point. 
The posterior maxillary bones are triangular in shape, thick behind, and 
presenting thin edges in front. The anterior maxillary bones 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 bone has an irregularly triangular shape, 
presenting its broad base forwards, and is connected with the temporal, 
posterior maxillary, and lachrymal bones. The lachrymal bones form the 
internal corners of the orbits, where they are very thin, and are hollowed 
out to receive the lachrymal sac, and give passage to its duct. The palate 
bones are of a very irregular shape, and are connected with the frontal, 
gthmoid, sphenoid, posterior maxillary, inferior turbinated bones, and 
vomer. The turbinated bones, two in each nasal cavity, are attached to 
its outer walls one above the other, and appear to be intended merely for 
the purpose of extending the surface for the expansion of the olfactory 
nerve. The vomer resembles in shape the share of the plough, after 
which it is named, and rises up in the middle line of the back of the 
division between the nostrils. 
