ANATOMY OF T1IE HOUSE. 
139 
Form. — Broad and fiat; terminating, inferiorly, in a semicircu¬ 
lar border, from which it narrows, upwards. 
Attachment. — Superiorly, to the pterygoid process, and crus of 
the sphenoid bone, to the palate bone, and to the tuberosity of the 
superior maxillary bone: inferiorly, to the fossa which it occu¬ 
pies, and around the angle of the jaw. 
Relation. —Externally, with the branch of the jaw, and poste¬ 
rior maxillary nerve and blood-vessels; internally, with the digas- 
tricus, hyoideus, stylo-pharyngeus, the os hyoides, the larynx, 
the anterior portion of the parotid gland, the submaxillary vessels, 
and the ninth and recurrent nerves: anteriorly r with the mylo- 
hyoideus and gustatory nerve; posteriorly, with the parotid gland, 
guttural cavities, and the next muscle: superiorly, with the base 
of the cranium; inferiorly, with the stylo-maxillaris and the skin. 
Direction. —Divergent, from above, downwards. 
Structure. —Fleshy, plenteously intersected with tendon. 
Action. —To raise the jaw. If one act alone, the jaw, in being- 
closed, will be drawn to one side: the alternate action of the two 
produces the lateral movement of the jaw which is so effectual in 
comminuting the food. 
PTERYGOIDEUS EXTEENUS. 
Situation. —Above and behind the former. 
Form. —Short, thick, cylindrical. 
Attachment. —Anteriorly, to the ala and crus of the sphenoid ; 
posteriorly, to the roughened depression upon the inner side of 
the jaw, at the root of the condyle. 
Relation. —Anteriorly, inferiorly, and internally, the preceding 
muscle, and the posterior maxillary nerve; superiorly, the orbit; 
posteriorly, the articulation of the jaws; externally, the neck of 
the jaw. 
Direction. —Oblique: from behind, forwards; and from with¬ 
out, inwards. 
Structure. —Fleshy, with slight tendinous intersections. 
Action. —To assist in the elevation of the jaw; and, at the same 
time, to draw it forwards : it is the antagonist in particular of the 
stylo-maxillaris. 
6.—HYOIDEAL REGION. 
The muscles in this region, and those remaining to be described, 
belonging to the head, are comprehended within the inter-max¬ 
illary space —between the branches of the lower jaw. 
dig ASTRICUS* —Portion of the Stylo-maxillaris. 
Situation. —Along the inner side of the lower jaw. 
