198 THE MUSCLES. 



Action. When the superior is the fixed point, it carries the entire 

 anterior limb forward. This muscle, therefore, plays a very important 

 part in locomotion ; as it is called into action when the animal raises the 

 fore-limb in getting over the ground. If the fixed point of the muscle 

 is the limb, it inclines the head and neck to one side. 



3. Sterno-maxillaris. (Figs. 102, 10; 114, 4.) 

 Synonym. The sterno-mastoideus of Man and a large number of the lower animals. 



Form Structure Situation Direction Attachments. A long narrow 

 muscle, almost entirely fleshy, and terminated at its upper extremity by a flat- 

 tened tendon ; situated in front of the neck, beneath the cuticularis, and 

 parallel to the anterior border of the superficial portion of the mastoido- 

 humeralis, from which it is separated by a space that lodges the jugular 

 vein ; attached, inferiorly, to the cariniform cartilage of the sternum fixed 

 insertion ; and superiorly movable insertion to the curved portion of the 

 posterior border of the maxillary bone by its terminal tendon. 



Relations. The muscle is covered by the cuticularis colli, and the 

 parotid gland. It covers the trachea, the subscapulo-hyoideus, sterno- 

 hyoideus, sterno-thyroideus, and the maxillary gland. Its external border, 

 parallel to the anterior border of the mastoido-humeralis, forms with it a 

 longitudinal depression termed the jugular furrow, because it lodges the 

 vein of that name. Its inner border is intimately united, in its lower third, 

 to that of the opposite muscle. 



Action. It directly flexes the head, when acting in concert with its 

 congener ; but alone it turns it to one side. Lafosse and Eigot have wrongly 

 considered this muscle as a depressor of the lower jaw. Bourgelat has 

 correctly stated that it cannot move this jaw independently. (Percivall says 

 that the pair will assist in opening the mouth ; and Leyh asserts that when 

 the mouth is closed, each muscle will act as a flexor to the head.) 



4. Sterno-hyoideus. 5. Sterno-thyroideus. (Fig. 114, 6, 7.) 

 (Synonym. The sierno-thyro-hyoideus of Percivall.} 



Form Structure Situation Attachments. Small, ribbon- shaped, long, 

 and slender muscles ; digastric ; situated in front of the trachea ; confounded 

 at their inferior extremity and united to those of the opposite side, so as to 

 form a single fasciculus which is attached to the cariniform cartilage of the 

 sternum -fixed insertion ; isolated from each other above the tendon which 

 makes them digastric, and terminating by their superior extremity movable 

 insertion : the first, on the inferior surface of the body of the hyoid bone in 

 common with the subscapulo-hyoideus ; the second, on the posterior border 

 of the thyroid cartilage. 



Relations. Covered by the sterno-maxillaris and the cuticularis muscle, 

 they cover the anterior face of the trachea. 



Action. Depressors of the hyoid bone and larynx. 



6. Omo-hyoideus or Subscapulo-hyoideus. (Figs. 102, 11 ; 114,5.) 

 Synonyms. Hyoideus Bourgelat. (Subscapulo-liyoideus Percivall.) 



Form Structure Situation Direction. This muscle forms a thin and 

 wide band, almost entirely fleshy, oblique forwards and upwards, extending 

 from the scapulo- humeral angle to the intermaxillary space, and applied to 

 the side of the trachea, whose direction it slightly crosses. 



