PERIORBITAL MUSCLES 



335 



The dilator naris posterior is a thin, triangular muscle which lies on the side of the wing 

 of the nose. It arises from the skin of the naso-labial groove and is attached to the inferior 

 border of the wing of the nose. 



The dilator naris anterior is a very small, thin muscle which runs from the lower margin 

 of the cartilage at the front of the wing of the nose to the skin. It is not usually clearly marked. 



Nerve-supply. — The muscles of this group are suppHed by the infra-orbital and buccal 

 branches of the facial nerve. 



Actions. — The transverse portion of the nasalis (compressor naris) acts with the angular 

 head (levator labii superioris alseque nasi) of the quadratus labii superioris in drawing lateral- 



FiG. 344. — The Deeper Muscles of the Face and Neck. 



Corrugator 



Procerus 

 Quadr. labii 

 sup. caput 

 angulare 



Caput infra- 



orbitale / 



Nasalis, pars_Z_ 

 transversa 

 Caninus 

 Depressor 

 septi nasi 

 Nasalis, pars 

 alaris 

 Orbicularis oris 

 Buccinator 



Triangularis 

 Quadratus la- 

 bii inferioris 

 Mentalis 

 Mylo-hyoid 

 Anterior belly 

 of digastric 



Temporal 



Zygomaticus 



Posterior belly 

 of digastric 



Splenius capitis 

 Stylo-hyoid 



Sterno-cleido- 

 mastoid 



Levator scapulae 



Scalenus anterior 





Scalenus 

 medius 



Omo- 

 hyoid 



A\ V'lla^ 



ward and up the lateral margin of the wings of the nose, and gives rise to the expression of sen- 

 suality. (Poirier.) This accords with the electrical experiments of Duchenne. However, 

 acting in conjunction with the alar portion, the transverse portion of the nasalis may constrict 

 the nostrils. The alar portion (depressor alse nasi) of the nasalis and the depressor septi nasi 

 draw down the nostril. The former tends to contract it from side to side, the latter from front 

 to back, and at the same time to depress the tip of the nose. They play a part in the expression 

 of anger and of pain. The functions of the other muscles are indicated by their names. 



Variations. — The muscles of the nose vary considerably in extent of development, and one 

 or more may be absent. Authors differ considerably in their description of several of the 

 muscles. The anomalus is a longitudinal muscle strip occasionally found running from the 

 frontal process to the body of the maxilla near the lateral margin of the nasal aperture. 



(e) PERIORBITAL MUSCLES 

 (Figs. 341, 344) 



The muscles which encircle the orbit constrict the entrance of the orbit so as 

 to shut out Hght and protect the eye against foreign bodies. To these belong 



