156 AURICULAR GROUP. 



The internal pterygoid is a thick quadrangular muscle. It arises 

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

 inserted into the ramus and angle of the lower jaw : it resembles 

 the masseter in appearance and direction, and was named by 

 Winslow the internal masseter. 



Relations. By its external surface with the internal pterygoid, 

 the inferior 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 and 

 superior constrictor of the pharynx with its fascia ; and by its pos- 

 terior border with the parotid gland. 



Actions. The maxillary muscles are the active agents in masti- 

 cation, and form an apparatus 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 

 becomes an important auxiliary in deglutition. The temporal, the 

 masseter, and the internal pterygoid are the bruising muscles, draw- 

 ing the lower jaw against the upper with great force. The two 

 latter, by the obliquity of their direction, assist the external ptery- 

 goid 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. 



8. 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 operation must be performed with care, otherwise the muscles, 

 which are extremely thin, will be raised with the superficial fascia. 



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 attrahens aurem (anterior auris,) also triangular, arises from 

 the edge of the aponeurosis of the occipito-frontalis ; and is inserted 

 into the anterior part of the concha, covering in the anterior and 

 posterior temporal arteries. 



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

 by the internal with the temporal aponeurosis and with the temporal 

 artery and veins. 





