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 quadratus and pterygoidean against the palatines. 



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

 goideus medialis.i) 



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 iii closing the jaw. 



Pterygoideus Extemus. (Synonym. — Pterygoideus lateralis.) 



Location. — Supero-extemal 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 



' According to international veterinary nomenclature- 



