382 



tears are sucked along the lacrimal canals into it. The lacrimal part of the Orbicularis oculi 

 draws the eyelids and the ends of the lacrimal canals medialward and compresses them against 

 the surface of the globe of the eye, thus placing them in the most favorable situation for receiving 

 the tears; it also compresses the lacrimal sac. The Corrugator draws the eyebrow downward 

 and medialward, producing the vertical wrinkles of the forehead. It is the "frowning" muscle, 

 and may be regarded as the principal muscle in the expression of suffering. 



m. THE MUSCLES OF THE NOSE (Fig. 378). 

 The muscles of the nose comprise: 



Procerus. Depressor septi. 





Nasalis. 



Dilatator naris posterior. 

 Dilatator naris anterior. 



The Procerus (Pyramidalis nasi) is a small pyramidal slip arising by tendinous 

 fibers from the fascia covering the lower part of the nasal bone and upper part 

 of the lateral nasal cartilage; it is inserted into the skin over the lower part of 

 the forehead between the two eyebrows, its fibers decussating with those of the 

 Frontalis. 



The Nasalis (Compressor naris) consists of tw r o parts, transverse and alar. The 

 transverse part arises from the maxilla, above and lateral to the incisive fossa; 

 its fibers proceed upward and medialward, expanding into a thin aponeurosis 

 which is continuous on the bridge of the nose with that of the muscle of the oppo- 

 site side, and with the aponeurosis of the Procerus. The alar part is attached by 

 one end to the greater alar cartilage, and by the other to the integument at the 

 point of the nose. 



The Depressor septi (Depressor alee nasi) arises from the incisive fossa of the 

 maxilla; its fibers ascend to be inserted into the septum and back part of the ala 

 of the nose. It lies between the mucous membrane and muscular structure of 

 the lip. 



The Dilatator naris posterior is placed partly beneath the Quadratus labii 

 superioris. It arises from the margin of the nasal notch of the maxilla, and from 

 the lesser alar cartilages, and is inserted into the skin near the margin of the 

 nostril. 



The Dilatator naris anterior is a delicate fasciculus, passing from the greater 

 alar cartilage to the integument near the margin of the nostril; it is situated in 

 front of the preceding. 



Variations. These muscles vary in size and strength or may be absent. 



Nerves. All the muscles of this group are supplied by the facial nerve. 



Actions. The Procerus draws down the medial angle of the eyebrows and produces transverse 

 wrinkles over the bridge of the nose. The two Dilatatores enlarge the aperture of the nares. 

 Their action in ordinary breathing is to resist the tendency of the nostrils to close from atmos- 

 pheric pressure, but in difficult breathing, as well as in some emotions, such as anger, they con- 

 tract strongly. The Depressor septi is a direct antagonist of the other muscles of the nose, drawing 

 the ala of the nose downward, and thereby constricting the aperture of the nares. The Nasalis 

 depresses the cartilaginous part of the nose and draws the ala toward the septum. 



IV. THE MUSCLES OF THE MOUTH. 



The muscles of the mouth are : 



Quadratus labii superioris. 



Caninus. 



Zygomaticus. 



Mentalis. 



Risorius. 



Quadratus labii inferioris. 

 Triangularis. 

 Buccinator. 

 Orbicularis oris. 



