MUSCLES OF THE TRUNK. 285 



2. Temporalis. 



Synonyms. — Temporo-maxillaria — Girard. 



Situation — Form — Structure. — Situated in the temporal fossa, to which it is 

 moulded, and which it fills, this muscle is flattened from above to below, divided 

 by strong tendinous intersections, and covered by a nacrous aponeurotic layer. 



Attachments. — It takes its origin : 1. In the temporal fossa and on the bony 

 crests which margin it. 2. By a wide fasciculus, paler than the other portion of 

 the muscle, but not unconnected with it, from the imprints situated behind the 

 crest surmounting the orbital hiatus. It terminates on the coronoid process and 

 the anterior border of the branch of the lower jaw. 



Relations. — This muscle covers the temporal fossa, and is covered by the 

 attoUens muscles, scutiform cartilage, internal scuto-auricularis, the fatty cushion 

 at the base of the ear, and by another adipose mass which separates it from the 

 ocular sheath. Its deep fasciculus responds, by its internal face, to the two 

 pterygoid muscles. 



Action. — It brings the lower jaw in contact with the upper, by acting as a 

 lever of the first kind ; but the orbital portion of the muscle elevates the inferior 

 maxilla and moves it laterally by a lever of the third kindo 



3. Pterygoideus Internus. 

 Synonyms. — Portion of the spheno-maxillaris of Bourgelat. 



Sitimtion — Form — Structure.— Sit\ia.ted in the intermaxillary space, opposite 

 the masseter, the pterygoideus internus, although not so strong as that muscle, 

 yet so closely resembles it in form and structure as to be named by "Winslow the 

 internal masseter. 



Attachments. — 1. To the palatine crest and subsphenoidal process— ;/?a;e^ 

 insertion. 2. In the hollow excavated on the inner face of the branch of the 

 lower jaw — movable insertion. 



Relations. — Outwardly, with the pterygoideus-externus, the orbital fasciculus 

 of the temporal, the maxillo-dental nerves, mylo-hyoideal, and lingual muscles, 

 arteries and veins, and the inner surface of the bone which receives its movable 

 insertion. Inwardly, with the tensors palati— external and internal, the 

 guttural pouch, the hyoideus magnus, hyoid bone, digastricus, the hypoglossal 

 and glosso-pharyngeal nerves, glosso-facial artery and vein, the hyoglossus longus 

 and brevis muscles, the laryngo-pharyngeal apparatus, the Stenonian duct, and 

 the submaxillary glands. 



Action. — It is an elevator of the lower jaw, and also gives it a very marked 

 lateral or diductive motion. If the left muscle acts, this movement carries the 

 inferior extremity of the lower jaw to the right ; if it be the right muscle, then 

 in the contrary direction. 



4. Pterygoideus Externus. 



(Synoraj/w.— Portion of the spheno-maxillaris of Bourgelat. 



Form — Situation — Strmture — Attachments. — A small, short, and very thick 

 muscle, situated within and in front of the temporo-maxillary articulation, 

 formed of shghtly tendinous fasciculi which leave the inferior face of the 

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