182 MAXILLARY GROUP. 



lower jaw, and inserted by its apex into the angle of the mouth, where it 

 is continuous with the levator anguli oris and zygomaticus major. 



Relations. By its superficial surface with the integument ; and by its 

 deep surface with the depressor labii inferioris, the buccinator, and tne 

 branches of the mental nerve and artery. 



The LEVATOR LABII INFERIORIS (levator menti) is a small conical slip 

 of muscle arising from the incisive fossa of the lower jaw, and inserted 

 into the integument of the chin. It is in relation with the mucous mem- 

 brane of the mouth, with its fellow, and with the depressor labii inferioris. 



fictions. The depressor labii inferioris draws the lower lip directly 

 downwards, and at the same time a little outwards. The depressor an- 

 guli oris, from the radiate direction of its fibres, will pull the angle of the 

 mouth either downwards and inwards, or downwards and outwards, and 

 be expressive of grief; or acting with the levator anguli oris and zygo- 

 maticus major, it will draw the angle of the mouth directly backwards. 

 The levator labii inferioris raises and protrudes the integument of the 

 chin. 



7. Maxillary group. Masseter, 



Temporalis, 

 Buccinator, 

 Pterygoideus externus, 

 Pterygoideus internus. 



Dissection. The masseter has been already exposed by the preceding 

 dissection. 



The MASSETER (fxarftfaofjuxi, to chew,) is a short, thick, and sometimes 

 quadrilateral muscle, composed of two planes of fibres, superficial and 

 deep. The superficial layer arises by a strong aponeurosis from the 

 tuberosity of the superior maxillary bone, the lower border of the malar 

 bone and zygoma, and passes backwards to be inserted into the ramus 

 and angle of the inferior maxilla. The deep layer arises from the poste- 

 rior part of the zygoma, and passes forwards, to be inserted into the 

 upper half of the ramus. This muscle is tendinous and muscular in its 

 structure. 



Relations. By its external surface with the zygomaticus major and 

 risorius Santorini muscle, the parotid gland and Stenon's duct, the trans- 

 verse facial artery, the pes anserinus and the integument. By its internal 

 surface with the temporal muscle, the buccinator, from which it is separated 

 by a mass of fat, and with the ramus of the lower jaw. By its posterior 

 border with the parotid gland ; and by the anterior border with the facial 

 artery and vein. 



Dissection. Make an incision along the upper border of the zygoma, 

 for the purpose of separating the temporal fascia from its attachment. Then 

 saw through the zygomatic process of the malar bone, and through the 

 root of the zygoma, near to the meatus auditorius. Draw down the 

 zygoma, and with it the origin of the masseter, and dissect the latter 

 muscle away from the ramus and angle of the inferior maxilla. Now re- 

 move the temporal fascia from the rest of its attachment, and the whole of 

 the temporal muscle will be exposed. 



The TEMPORAL is a broad and radiating muscle occupying a considera- 

 nle extent of the side of the head and filling the temporal fossa. It is 

 covered in by a very dense fascia (temporal fascia) which is attached along 



