152 DISSECTION OF THE DOG 



M. tragicus lateralis springs from the border of the mandible between the 

 condyloid and angular processes. 



M. tragicus medialis joins the tragus to the base of the conchal cartilage. 



M. helicis joins helix and antitragus. 



M. transverstjs ATJRicuL/E. — The transverse muscle is a band of fibres 

 lying on the conchal cartilage close to the insertion of the long levator. 



M. antitragicus consists of a few fibres placed immediately aboral to the 

 attachment of the inferior auricular muscle, and runs from the tragus to the 

 antitragus. 



A. aurictjlaris posterior. — The main artery of the external ear is the 

 posterior auricular, a branch of the external carotid. Commencing on a level 

 with the hyoid bone, this artery runs to the base of the ear underneath the 

 parotid gland, and is distributed to the aboral and medial portions of the ear. 



A. atjricularis anterior. — The anterior auricular artery is a branch of the 

 superficial temporal from which it is derived on a level with the zygoma. The 

 vessel ramifies over the oral and medial parts of the external ear. 



N. aurictjlaris posterior. — The posterior auricular nerve leaves the 

 seventh cerebral nerve under the parotid gland and divides into branches which 

 follow those of the posterior auricular artery. 



X. auricularis internus. — Also a branch of the seventh cerebral nerve, 

 the internal auricular pierces the deep lateral part of the conchal cartilage in 

 the interior of which it is distributed. 



The temporal division of the auriculo-palpebral branch of the seventh nerve 

 supplies the oral part of the ear. 



The auricular branch of the second cervical nerve is distributed over the 

 lateral and aboral part of the ear ; and the occipital branch of the first cervical 

 nerve spreads out over the medial surface. 



M. occipitalis. — Although not belonging to the ear, the occipital muscle 

 may be examined at this stage of the dissection. The muscle is a narrow, 

 thin band running longitudinally from the superior nuchal line of the occipital 

 bone and the sagittal crest of the parietal into the fascia which is blended with 

 the periosteum of the frontal bone. 



The muscles of the dorsal part of the neck must now be examined. 

 M. si'LENius. — The splenius muscle is triangular, with its apex caudal and 

 its base at the occipital bone. The origin of the muscle extends as far caudal as 

 the fifth or sixth thoracic spinous process, and is continued along the middle 

 dorsal line throughout the cervical region. At first the origin is aponeurotic, 

 but from the first or second thoracic spine onwards it is fleshy. The insertion 

 of the muscle is into the occipital bone and mastoid part of the temporal bone- 

 About the level of the atlas the fibres of the splenius are closely connected 

 with the tendon of the longissimus capitis muscle. 



