222 THE MUSCLES. 



10. The Middle (Intermediate) Anterior Muscle. 



Synonyms. Medius anterior Bourgelat. Myrtiformis of Man. (Depressor labii 

 superioriPercivall. Incisive muscle of the upper lip Leyh. A portion of the 

 orbicularis, according to Bigot.) 



Bourgelat thus names a deeply-situated muscle which is fixed to the 

 inner face of the premaxillary bone, above the incisor teeth, and whose 

 fibres ascend to meet those of the posterior portion of the small super- 

 maxillo-nasalis muscle, to terminate with them on the anterior appendix of 

 the inferior turbinated bone ; some fibres become lost in the lip. It is 

 regarded as a dilator of the entrance to the nasal fossa. 



To study this muscle, it is necessary to raise the upper lip and remove the mucous 

 membrane covering it. It may be dissected at the same time as the bony attachments of 

 the superficial plane of the alveolo-labialis muscle. 



11. Maxillo-labialis. (Fig. 110, 28.) 



Synonyms. Depressor labii inferioris Eigot. A dependency of the buccinator of 

 Man. (Dep-essor labii inferioris Percivall. Inferior maxillo-labialis Leyh. Depressor 

 anguli oris of Man.) 



Situation Direction Form Structure. Situated along the inferior 

 border of the alveolo-labialis, whose direction it follows, tbis muscle forms a 

 long narrow fasciculus, terminating inferiorly by an expanded tendon. 



Attachments. 1, By its superior extremity, to the anterior border of 

 the lower jaw, in common with the deep plane of the alveolo labialis fixed 

 origin ; 2, By its terminal tendon, to the skin of the lower lip movable 

 insertion* 



Relations. Outwardly, with the masseter and the facial portion of 

 cuticularis of the neck ; inwardly, with the maxillary bone ; in front, with 

 the alveolo-labialis muscle, with which it is directly united in its upper two- 

 thirds. 



Actions. It separates the lower from the upper lip, and pulls it to the 

 side if one alone acts. 



12. Mento-ldbialis or Muscle of the Chin. (Fig. 110, 29.) 



(Anonyms. Percivall appears to describe this and the next muscle as one. It is the 

 quadratus menti of Man.) 



This name is given to a musculo-fibrous nucleus, forming the base of the 

 rounded protuberance beneath the lower lip in front of the beard. This 

 single nucleus is confounded, in front, with the orbicularis of the lips, and 

 receives into its upper face the insertion of the two posterior middle muscles 

 (levatores menti). 



13. Middle (Intermediate} Posterior Muscle. 



Synonyms. Medina posterior Bourgelat. (Levator menti Percivall. Incisive muscle 

 of the lower Up Leyh.) 



Bourgelat describes, by this name, a small muscular fasciculus, analogous 

 in every respect to the medius anterior. This little muscle takes its origin 

 from the external surface of the body of the lower jaw, beneath the inter- 

 mediate and corner incisors ; from thence it descends into the texture of the 

 lip, to unite with that of the opposite side on the upper face of the mento- 

 labialis. Several authors have described it as a dependent of the last muscle. 



