992 
Journal of Agricultural Research 
Vol. XXVIII, No. 10 
it may be of some help in certain forward movements of the mandible, although 
this is not the case with many mammals, including man. 
Temporalis. —This muscle may also be divided into a superficial and a (Jeep 
portion. The former (see fig. 5, a), well developed in the present animal, arises 
along the lambdoidal crest and thence forward along the temporal ridge to the 
posterior termination of the interorbital constriction. It then descends an¬ 
teriorly and laterally, wholly within the orbit, to an insertion upon the anterior 
Fig. 6—Superficial portion of the masseter major (masseter superficialis removed) 
edge of the coronoid process, and thence anteroinferiorly to the junction of the 
latter process with the main body of the ramus. The-anterior portion of the 
insertion is wholly by a thin, aponeurotic sheet. The deep part (see fig. 4, a) 
arises upon the postorbital process and inserts upon the medial side of the 
coronoid process from its tip to the temporal fossa of the mandible (between 
the molars and the coronoid process). 
Fig. 7.—Head, showing the deep portion of masseter major, including the anterior portion of the ante- 
orbital branch (masseter superficialis, zygomatica, and the superficial part of major, removed) 
The temporal is a very powerful muscle and is used not only for closing the 
mouth, but to some extent for drawing the mandible backward. 
Pterygoideus externus. —This muscle arises from the lateral side of that 
portion of the external pterygoid plate anterior to the foramen rotundum, and 
inserts upon the inferior border of the medial process on the head of the 
condyle. 
Pterygoidetjs internus. —This arises from the pterygoid fossa and inserts 
upon the medial surface of the angular process of the mandible. Both this 
muscle and the pterygoideus externus are used in lateral movements of the 
jaw, such motion being produced by their alternate action first from one side 
then from the other. 
