POSTERIOR MAXILLARY GROUP. Ii7 



Action. It compresses the upper lip, and perhaps assists iu 

 dilating the nostril. 



LEVATOR LABII IXFERIORIS. 

 (Levat&r Menti.) 



Situated on the inner surface of the under lip, below the 

 mucous membrane, it is like the preceding in shape. 



Origin. From the alveoli of the inferior maxilla, between the 

 lateral incisors and tushes. 



Insertion. The under lip by diverging fibres. 



Action. It elevates the under lip and chin, and presses the 

 lip on the teeth. 



DEPRESSOR LABII IXFERIORIS. 



(AlaxiUo-labialis. ) 

 (PL. H. 10. FIG. 70. h.) 



Situated along the surface of the lower jaw, it is in shape long 

 and pyramidal. 



Origin. Posteriorly, in common with the buccinator, from 

 the alveolar tuberosity, and the superior border of the inferior 

 maxilla, behind the molar alveoli. 



Insertion. The infero-lateral part of the under lip by a flat 

 tendon. 



Action* To depress the under lip. 



POSTERIOR MAXILLARY GROUP. 



The muscles constituting this group are chiefly those of masti- 

 cation, which act upon the temporo-maxillary joint. They areas 

 follows : 



Masseter. 



Temporalis. 



Stylo-maxillaris. 



Pterygoideus interims. 

 Pterygoideus extti 

 Disrastricus. 



* [While dissecting at the Edinburgh Veterinary College in December, 1868, 

 particularly struck with the .action of this muscle ; its tendon subdivides 

 in the areolar and muscular tissue of chin and posterior lip, and its action is 

 not quite to depress the under lip, but to elevate the chin and lower lip, and 

 thus separate the lower lip from the lower incisors. This is the opinion, I find, 

 recorded by the late Professor Goodsir in his posthumous manuscript. ED 

 First Edition.] 



