THE MUSCLES OF THE HEAD. 107 
Origin from the pad upon which the whiskers rest. The 
fibres diverge and have their 
Jnsertion upon the wing of the nose and into the skin of the 
upper lip near the median line. 
Action.—-Dilator of the nares and elevator of the upper lip. 
M. ‘‘moustachier’’ (Str.-D.) (probably corresponds to 
one of the Mm. incisivi).-—lt lies on the upper lip near the 
median line. 
Origin from the outer surface of the premaxilla near the 
suture along the ventral border of the narial opening. The 
fibres diverge and pass caudad into the upper lip within the 
superficial fibres of the orbicularis oris. 
Jnsertion.—The skin of the upper lip just craniad of the 
whiskers. Some of the fibres pass into the pad on which the 
whiskers rest. 
Action.—lIt carries the lip craniad. 
M. quadratus labii inferioris.—A thin flat band extending 
almost the length of the lower lip. 
Origin from the alveolar border of the mandible, between 
the molar tooth and the canine. The fibres pass dorsad into 
the lower lip, where they intermingle with those of the orbi- 
cularis oris. The muscle is perhaps not constant. 
Action.—Depressor of the lower lip. 
Sometimes a few fibres arising from the cranial portion of 
the alveolar border of the mandibula pass mediad, seeming to 
join corresponding fibres from the opposite side. Such fibres 
would constitute a M. transversus menti. 
B. DreEP MUSCLES OF THE HEAD. 
(a) Muscles of Mastication. 
M. digastricus (Fig. 65, 4).—The digastric is a thick pris- 
matic muscle lying mediad of the angle of the lower jaw, con- 
necting it with the base of the skull. 
Origin by fleshy fibres from the outer surface of the jugular 
process of the occipital bone, and by a thin tendon from the 
tip of the mastoid process and from the ridge between the 
mastoid and the jugular processes. The muscle passes craniad, 
becoming at the same time broader and more voluminous. 
