STERNO-CLEIDO-MASTOIDEUS. 159 



scapulae, splenii, and posterior belly of the digastric muscle ; with 

 the phrenic nerve, and the posterior, and supra-scapular artery ; with 

 the deep lymphatic glands, the sheath of the common carotid artery 

 and internal jugular vein, the descendens noni nerve, the external 

 carotid artery and its posterior branches, the commencement of the 

 internal carotid artery ; with the cervical plexus of nerves, the 

 pneumogastric, the spinal accessory, the hypoglossal, the sympa- 

 thetic and the facial nerve, and with the parotid gland. It is 

 pierced on this aspect by the spinal accessory nerve and by the 



Fig. 71* 



branches of the mastoid artery. The anterior border of the muscle 

 is the posterior boundary of the great anterior triangle, the other 

 two boundaries being the middle line of the neck in front, and the 

 lower border of the jaw above. It is the guide to the operations 

 for the ligature of the common carotid artery and arteria innomi- 

 nata, and for ccsophagotomy. The posterior border is the anterior 

 boundary of the great posterior triangle ; the other two boundaries 

 being the anterior border of the trapezius behind, and the clavicle 

 below. 



Actions. The platysma produces a muscular traction on the 

 integument of the neck, which prevents it from falling so flaccid in 



* The muscles of the anterior aspect of the neck ; on the left side the superficial 

 muscles are seen, and on the right the deep. 1. The posterior belly of the digastricus 

 muscle. 2. Its anterior belly. The aponcurotic pulley, through which its tendon is 

 seen passing, is attached to the body of the os hyoidcs 3. 4. The stylo-hyoideus mus- 

 cle, transfixed by the posterior belly of the digastricus. 5. The mylo-hyoideus. 6. 

 The genio-hyoideus. 7. The tongue. 8. The hyo-glossus. 9. The stylo-glossus. 

 10. The stylo-pharyngeus. 11. The sterno .mastoid muscle. 12. Its sternal origin. 

 13. Its clavicular origin. 14. The sterno-hyoid. 15. The sterno-thyroid of the right 

 side. 16. The thyro-hyoid. 17. The hyoid portion of the omo-hyoid. 18, 18. Its 

 scapular portion ; on the left side, the tendon of the muscle is seen to be bound down 

 by a portion of the deep cervical fascia. 19. The clavicular portion of the trapezius. 

 20. The scalenus anticus, of the right side. 21. The scalenus posticus. 



