MUSCLES OF RIGHT SIDE OF TRUNK AND HEAD 9 1 



vertebrae; to spinous process of the next four or more thoracic 

 vertebrae. 



60. Levatores costarum mm. : Ends of transverse processes 

 of thoracic vertebrae; caudoventrally to lateral surface, near 

 angle, of next rib caudad. Elevates the ribs ; therefore functions 

 in inspiration. Method: To get at these muscles it is necessary 

 to cut a '' window" about an inch long through the longissimus 

 m. (596) in the region of the fourth to eighth thoracic vertebrae 

 and probe the levator m. 



61. Sternothyroid (sternothyroideus) m.: Sternum; to 

 lateral side of thyroid of larynx. A narrow, slip of a muscle. 

 Transect. 



62. Sternohyoid (sternohyoideus) m.: Dorsal surface of 

 manubrium and first pair of costal cartilages; to greater cornu 

 of hyoid. Right and left muscles are fused together for most 

 of their length and thus form a wide ribbon-like muscle which 

 envelops the ventrolateral surfaces of the trachea from the 

 sternum to the cranial margin of the thyroid cartilage. At this 

 point the muscle bifurcates, each limb narrowing to its insertion 

 onto a greater cornu of the hyoid bone. Do not transect this 

 muscle. 



B. MUSCLES OF THE HEAD 



(Nos. 63-64) 

 Only two muscles of this very difficult region will be required ; 

 however, the student should spend some time studying the 

 muscles of mastication in reference books. 



63. Masseter muscle: Zygomatic arch mainly; to margin and 

 lateral side of angle and ramus of mandible. Elevates the 

 mandible. Note the relations of the parotid duct, p. 92 and 

 facial nerve, p. 122. Method: Make an incision from the 

 external auditory meatus cranioventrad through the belly of 

 the masseter to the mandibular ramus with the cartilage knife. 



64. Digastric (digastricus) m.: Occipital bone and mastoid 

 process ; to ventromedial margin of mandible near the symphysis. 

 Depresses the mandible. Transect. 



