78 ANATOMY OF THE DOMESTIC FOWL 



the upper side of the pterygoid, and the other to the quadrato-ptery- 

 goidean articulation. 



Shape. Spindle-shaped. 



Relations. Anteriorly with the pterygoid. Internally and pos- 

 teriorly with the basi-sphenoid. Externally with the pterygoideus 

 internus. 



Action. Aids in raising the upper mandible by pulling forward 

 the quadra tus and pterygoidean against the palatines. 



Pterygoideus Internus (Fig. 17, No. B, 5). (Synonym. Ptery- 

 goideus median's. 1 ) 



Location. A muscular mass at the roof of the mouth. 



Origin. From the major part of the surface of the palatine bone 

 and the distal head and shaft of the pterygoid and the sphenoidal 

 projection. 



Insertion. By a tendon to the antero-internal part of the articular 

 part of the mandible. 



Shape.- Fusiform with a thick fleshy belly. 



Relations. Superiorly with the palatine, the pterygoid, and the 

 sphenoid bones. Inferiorly with the skin. 



Action. It aids in closing the jaw. 



Pterygoideus Externus. (Synonym. Pterygoideus lateralis.) 



Location. Supero-external to the pterygoideus internus. 



Origin. From the outer part of the extremity of the orbital proc- 

 ess of the quadrate. 



Insertion. The fibers pass downward, outward and forward and 

 are inserted to the inner part of the mandibular ramus. 



Shape. A small round bundle. 



Relations. Inferiorly with the pterygoideus internus. Externally 

 with the inferior maxilla. 



Action. Aids in closing the jaw. 



Digastricus (Fig. 17, No. B, 16). Location. Extends from the 

 basi-temporal to the side of the neck. 



Origin. From the external lateral angle of the basi-temporal. 



Insertion. Opposite the angle of the jaw the fibers spread out in 

 fan-like arrangement. The muscle meets its fellow of the opposite 

 side; extends longitudinally over the superior larynx, for some 

 distance down the neck. 



Shape. Thin and ribbon-shaped. 



Relations. Externally to the platysma myoides. The anterior 



1 According to international veterinary nomenclature- 



