184 AURICULAR GROUP. 



The external pterygoid muscle must now be removed, the ramus of the 

 lower jaw sawn through its lower third, and the head of the bone dislo 

 cated from its socket and withdrawn, for the purpose of seeing the ptery 

 goideus internus. 



The INTERNAL PTERYGOID is a thick quadrangular muscle. It arises 

 from the pterygoid fossa, and descends obliquely backwards, to be in- 

 serted into the ramus and angle of the lower jaw : it resembles the masse- 

 ter in appearance and direction, and was named by Winslow the internal 

 masseter. 



Relations. By its external surface, with the external pterygoid, the in- 

 ferior maxillary nerve and its branches, the internal maxillary artery and 

 branches, the internal lateral ligament, and the ramus of the lower jaw 

 By its internal surface, with the tensor palati, superior constrictor ana 

 fascia of the pharynx; and by its posterior border, with the parotid gland. 



Actions. The maxillary muscles are the 

 Fig. 108 * active agents in mastication, and form an ap- 



paratus beautifully fitted for that office. The 

 buccinator circumscribes the cavity of the 

 mouth, and with the aid of the tongue, keeps 

 the food under the immediate pressure of the 

 teeth. By means of its connexion with the 

 superior constrictor, it shortens the cavity of 

 the pharynx from before backwards, and be- 

 comes an important auxiliary in deglutition. 

 The temporal, the masseter, and the internal 

 pterygoid, are the bruising muscles, drawing 

 the lower jaw against the upper with great 

 force. The two latter, by the obliquity of their direction, assist the ex- 

 ternal pterygoid in grinding the food, by carrying the lower jaw forward 

 upon the upper ; the jaw being brought back again by the deep portion 

 of the masseter and posterior fibres of the temporal. The whole of these 

 muscles, acting in succession, produce a rotatory movement of the teeth 

 upon each other, which, with the direct action of the lower jaw against 

 the upper, effects the proper mastication of the food. 



S. Auricular Group. Attollens aurem, 

 Attrahens aurem, 

 Retrahens aurem. 



Dissection. The three small muscles of the ear may be exposed by 

 removing a square of integument from around the auricula. This opera- 

 tion must be performed with care, otherwise the muscles, which are ex 

 tremely thin, will be raised with the superficial fascia. They are best 

 dissected by commencing with their tendons, and thence proceeding in 

 the course of their radiating fibres. 



The ATTOLLENS AUREM (superior auris), the largest of the three, is a thin 

 triangular plane of muscular fibres arising from the edge of the aponeurosis 

 of the occipito-frontalis, and inserted into the upper part of the concha. 



It is in relation by its external surface with the integument, and by the 

 internal with the temporal aponeurosis. 



* The two pterygoid muscles. The zygomatic arch and the greater part of the ramus 

 nf the lower jaw Lave been removed, iri order to bring these muscles into view. i. 

 The spheroid origin of the external pterygoid muscle. 2. Its pterygoid origin. 3. Tha 

 internal pterygoid rnuscfe. 



