(c) 
(d) 
(e) 
(f) 
THE HEAD AND NECK. 241 
medial side of the reduced coronoid process. The muscle 
may be exposed by dividing the temporal portion of the 
posterior supraorbital ligament which holds its tendon in 
place; then divided. 
On account of the narrowness of the space lying between the two 
limbs of the mandible, and the great depth of its angle, it is necessary, 
in order to expose the surface for the deep dissection of the ventral portion 
of the head and neck, to remove one-half of the mandible entirely. Hence 
the following order: 
Divide the mandibular symphysis, and pass a knife along the 
medial surface of the bone to,be removed. The tip of the 
knife must be kept close to the bone, so that the underlying 
soft parts, excepc¢ for being divided, will be kept uninjured. 
The medial surface of the mandible should be clean when 
removed. The bone may be turned laterad and detached 
from the skull at the articulation. 
The structures appearing on the cut surface include the 
insertion of the digastricus and the margin of the mylohy- 
oideus; also: 
The pterygoideus internus muscle. Origin: Pterygoid 
process of the skull. Insertion: Ventral portion of the 
medial surface of the angle. 
The pterygoideus externus. Origin: Lateral plate of the 
pterygoid process. Insertion: Dorsal portion of the medial 
surface of the angle. Both muscles are strongly developed. 
The inferior alveolar artery (a. alveolaris inferior) lies be- 
tween the two pterygoidei. Its cut end marks the point of 
entrance into the mandible through the mandibular foramen. 
The corresponding inferior alveolar vein leaves the man- 
dible at this point. 
The inferior alveolar nerve (n. alveolaris inferior) accom- 
panies the inferior alveolar artery to the mandible. The con- 
tinuation of the nerve is the mental nerve. It appears at 
the mental foramen, and passes to the lower lip. 
The origin of the inferior alveolar nerve may be traced. It 
arises from the mandibular nerve (n. mandibularis), the 
third division of the fifth cranial or trigeminal nerve 
(n. trigeminus), which. also gives off anteriorly the stout 
lingual nerve to the tongue and posteriorly the slender 
