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, except 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 digastricas and the margin of the mylohy- 

 oideus; also: 



(c) The pterygoideus intern us muscle. Ofigin: Pterygoid 

 process of the skull. Insertion: Ventral portion of the 

 medial surface of the angle. 



(d) The pterygoideus extern US. Origin: Lateral plate of the 

 pterygoid process. Insertion: Dorsal portion of the medial 

 surface of the angle. Both muscles are strongly developed. 



(e) 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. 



(I) 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 a!lso gives off anteriorly the stout 

 lingual nerve to the tongue and posteriorly the slender 



