MUSCLES OF THE LOWER JAW. 387 
bones, and from the inferior part of the superior maxillary bone; at 
the cartilages of the nose the tendons, the one on the right side and 
the other on the left, blend together and unite in one common tendon 
which is inserted upon the superior part of the upper lip. Acton ts 
corrugate the upper lip, and thence to raise it. 
Caninus is situated over the two anterior molar teeth. Origin—from 
the superior maxillary bone, near its junction with the anterior maxilla. 
Insertion—to a roughened depression on the inferior maxillary bone, just 
behind the lower tush. Action—to assist in closing the mouth. 
DInaATATOR NARIS ANTERIOR is situated in front of and between the 
nostrils. Origin—from the supero-anterior surface of the os nasi. Inser- 
tion—to the anterior part of the alar cartilages, blending with the 
orbicularis oris. A ction—to raise the upper lip. 
NASALIS BREVIS LABIL SUPERIORIS is situated behind the nostrils, 
Origin—from the superior and anterior maxillary bones, and from the 
‘suture uniting them. Jnsertion—to the supero-anterior part of the septum 
nasi, and to the skin of the false nostrils. Action—to dilate the nostrils. 
BuccrnaTor is situated between the upper and lower jaws. Origin— 
from the tuberosity of the superior maxillary bone, and from the outer 
walls of the alveolar cavities of the upper molar teeth. Insertion—to 
the outer walls of the alveolar cavities of the lower molar teeth. In 
front it is blended with the orbicularis oris. Action—to draw back the 
angle of the lips, and tighten the outer wall of the mouth. 
RETRACTOR LABIL INFERIORIS is situated on the anterior part of the 
lower jaw. Orvigin—from the external part of the lower jaw, just behind 
the last molar tooth. /nserteon—to the inferior part of the lower lip. 
This muscle blends with the orbicularis oris. Action—to retract the 
lower lip. 
Naso TRANSVERSALIS is situated between the two alar cartilages. This 
muscle runs between the antero-internal borders of each cartilage to which 
it is attached, and its action tends to approximate them. 
DEPRESSOR LABII SUPERIORIS lies upon the anterior part of the upper 
jaw. Origin—from the anterior maxillary bone, and from the outer 
border of the alveoli of the incisor teeth, extending as far back as the 
tush. Jnsertion—to the upper lip and inferior nasal cartilages. Action 
—to assist in dilating the nostrils, and in retracting the upper lip. 
ORBICULARIS ORIS.—This sphincter muscle is situated within the border 
of the lips. Origin—from the outer surfaces of the superior and inferior 
~maxillary bones. Jnsertion—it interlaces with its own fibres at the angles, 
and is also attached to the glandular substance and skin of the lips. 
Action—to contract the opening of the lips, and compress them against 
the jaws. 
DEPRESSOR LABII INFERIORIS lies along the side of the lower jaw. 
Origin—from the side of the lower jaw, close to that of the buccinator. 
Jnsertion—into the fat of the prominence of the chin. 
LEVATOR MENT! is a little square muscle bracing the soft parts, covering 
the chin, up against the jaw. It arises from the edge of the alveolar pro- 
cess of the corner tooth on one side, passes beneath the chin, and meets 
there its fellow of the opposite side. 
MUSCLES WHOSE OFFICE IT IS TO MOVE THE LOWER 
JAW. 
TemporaLis is situated on the top and sides of the head. Origin--- 
from the occipital, parietal, squamous plate, and zygomatic process of the 
cc2 ; 
