162 MYOLOGY. 



from the angle of the maxilla, and a portion is inserted to the 

 orbicular muscle of the mouth, forming the Retractor anguli oris 

 (Risorius Santorini). Posteriorly it unites with the cervical por- 

 tion, which is likewise chiefly aponeurotic, commencing in front 

 of the neck by a thin muscular band, it joins its fellow in the 

 median line by a fibrous raphe, and covers the muscles of the 

 inferior cervical region. Above it becomes aponeurotic, and is 

 attached to the ligamentum nuchas, while infero-laterally it 

 becomes more fleshy, and is inserted to the. anterior portion of 

 the cariniform cartilage ; some describe this portion as a part of 

 the Levator humeri, the panniculus being firmly blended with 

 that muscle inferiorly. The thoracic portion is continuous with 

 the cervical at the sternum, and passes over the front of the 

 shoulder superiorly, covering its external side ; it is attached to 

 the dorsal spines together with the trapezius. The abdominal 

 portion forms a broad oval-shaped fleshy expansion, its fibres 

 running from the flank to the shoulder ; it is thick and fleshy 

 behind the arm, where it has a well-marked, flat tendinous attach- 

 ment to the skin, and below which a tendinous expansion pene- 

 trates between the chest and the limb, and is attached to the 

 Pectoralis inagnus and internal trochanter of the humerus. 

 Posteriorly, by a strong band, fleshy and aponeurotic, it reaches 

 the stifle joint and fascia of the thigh ; above, it reaches the 

 lumbar and dorsal spines, and below it becomes blended with the 

 abdominal fascia. 



Relation. It is related externally with the skin ; internally 

 with the superficial layer of muscles. 



Action. It corrugates the skin, and thus enables the animal 

 to expel insects and irritating bodies, its use being thus protec- 

 tive ; to some extent it also supports and binds down the subja- 

 cent muscles. 



THE HEAD. 



The muscles of this region may be divided into the following 



to " Anterior maxillary. 



Posterior maxillary. 

 Hyoidean. 

 Palpebral. 

 Auricular. 



In addition to these we have the Glossal, Pharyngeal, and 

 Laryngeal groups also associated with the head ; the two first of 



