BONES OF THE FACE—THE MAXILL 63 
the external opening of the facial canal, through which the facial nerve emerges. The 
bulla ossea is a considerable eminence situated centrally; it is thin walled and 
incloses a cavity which is part of the tympanum. The muscular process (Processus 
muscularis)! is a sharp spine which projects downward and forward from the an- 
terior part of the base; it gives origin to the tensor and levator palati muscles. 
Lateral to the root of the preceding is the small petrotympanic fissure (lissura 
petrotympanica) for the passage of the chorda tympani nerve. The osseous 
auditory or Eustachian tube (Tuba auditiva ossea) is a semicanal at the medial 
side of the root of the muscular process; it leads to the tympanum. At the medial 
side of the preceding is the slit-like orifice of the petrosal canal, which communi- 
cates with the facial canal. 
The apex projects upward and backward between the squamous temporal and 
the occipital bone. 
Development.—The squamous temporal develops in membrane. The pe- 
trous temporal may be regarded as consisting of petro-mastoid and tympanic parts. 
The latter includes the external acoustic process, the bulla ossea, and the muscu- 
lar process; it is developed in membrane. The petro-mastoid is developed in the 
cartilaginous ear capsule. Its petrous part consists of very dense bone which con- 
tains the labyrinth or internal ear and forms the medial wall of the tympanum. 
The auditory ossicles and the interior of the petrous temporal bone are described in the 
section on the organ of hearing. 
The temporal canal (Meatus temporalis)? is a continuation of the transverse 
groove which extends laterally from the base of the tentorium osseum. It is 
directed downward, forward, and somewhat outward, and opens externally in front 
of the root of the acoustic process. It is bounded by the squamous temporal 
laterally, the petrous behind, and the parietal in front and medially. Several 
foramina open from it into the temporal fossa. It contains a large vein (Vena 
cerebralis dorsalis), the continuation of the transverse sinus of the dura mater. 
The foramen lacerum (basis cranii) is a large, irregular opening in the cranial 
base, bounded medially: by: the basilar part of the occipital bone, laterally by the 
petrous temporal, and in front by the temporal wing of the sphenoid. It consists 
of a large anterior part (Foramen lacerum anterius), and a narrow posterior part 
(Foramen lacerum posterius). It transmits the internal carotid artery, the middle 
meningeal artery, the mandibular, ninth, tenth, and eleventh cranial nerves, and 
the ventral cerebral vein. 
In the fresh state the foramen is occupied by a dense fibrous membrane which is perforated 
by apertures for the various structures transmitted. Thus there are three openings in front for 
the internal carotid artery, the mandibular nerve, and the middle meningeal artery; these are 
named (from within outward) the foramen caroticum, ovale, spinosum. 
(B) BONES OF THE FACE 
The bones of the face (Ossa faciei) are the maxilla, premaxilla, palatine, 
pterygoid, nasal, lacrimal, malar, dorsal turbinate, ventral turbinate, vomer, mandi- 
ble, and hyoid. The last three are single, the others paired. 
THE MAXILLE 
The maxilla are the principal bones of the upper jaw and carry the upper 
cheek teeth. They are situated on the lateral aspect of the face, and articulate 
with almost all of the facial bones and the frontal and temporal also. For descrip- 
tion each may be divided into a body and two processes. 
1This has been termed the styloid process. It is not the homologue of the styloid proc- 
ess of man. 
? This is also known as the parieto-temporal canal. 
