76 A MANUAL OF ANATOMY. 



of the sternomastoid muscle, just above its middle. The 

 first passes upward diagonally across the sternomastoid to 

 the region of the parotid gland, the second runs parallel 

 with the posterior border of the sternomastoid to the side 

 of the head, and the third crosses the muscle directly for- 

 ward. 



There are several cutaneous nerves which descend 

 toward the chest. 



They issue from the posterior margin of the sternomas- 

 toid also, and pass to the sternum (sternal}, the clavicle 

 (clavicular), and to the shoulder (acromial). For a full 

 description of these several nerves, see the cervical plexus, 

 page 89. 



Sternocleidomastoid. Fig. 16. 



Origin. The inner head, from the upper part of the 

 manubrium ; the outer head, from the upper surface of the 

 inner third of the clavicle. 



Insertion. The mastoid process of the temporal, and the 

 outer half of the superior curved line of the occipital bones. 



Nerve Supply. From the deeper branches of the second 

 and third cervical nerves, and the spinal accessory, which 

 passes through the muscle on its way to the trapezius. 



Action. Acting from below. Both muscles will flex 

 the head and neck. One will flex the head laterally, and 

 rotate the chin to the opposite side. 



Acting from above. Will raise the clavicles and sternum, 

 and so act in inspiration. 



The spinal accessory and cervical branch to the trape- 

 zius muscle. These two nerves will be found as the fascia 

 is cleaned out between the sternomastoid and the trapezius 

 muscles. Figs. 16, 17. 



The first issues from the sternomastoid muscle at its 



