THE MUSCULAR SYSTEM. 137 



MUSCLES OF THE EAR (vide EAR). 



MUSCLES OF THE NECK. 

 SUPERFICIAL CERVICAL REGION". 



PLATYSMA MYOIDES. Origin, from the deep fascia over the 

 trapezius, deltoid,, and pectoral muscles, and from the clavicle 

 and acromion ; insertion, into the lower jaw and skin of the face ; 

 action, wrinkles the skin of the neck and protects the air-passages 

 and blood-vessels from external pressure, rudimentary in man; 

 nerves, branch of superficial cervical plexus and the facial. 



STERNO-CLEIDO-MASTOID. Origin, by two heads sternal 

 portion from the fore and upper part of the manubrium sterni, 

 the clavicular portion from the inner third of the upper border 

 of the clavicle, leaving a triangular interval; insertion, into the 

 mastoid process and outer two-thirds of the superior curved line 

 of the occipital bone; action, rotates and depresses the head; 

 nerves, spinal accessory and branches of the cervical plexus. 



INFRA-HYOID REGION". 



STERNO-HYOID. Origin, from upper and back part of the 

 manubrium sterni and inner extremity of the clavicle ; insertion, 

 into the lower border of the os hyoides; action, depresses the 

 hyoid bone; nerve, branch from the loop of communication be- 

 tween the descendens and communicans noni. 



STERNO-THYROID. Origin, posterior surface of manubrium 

 sterni; insertion, into oblique line of the surface of the thyroid 

 cartilage; action, depresses the larynx; nerve, branch from the 

 communicating loop above. 



THYRO-HYOID. Origin, from the oblique line on the sur- 

 face of the thyroid cartilage; insertion, into the greater cornu 

 and body of the hyoid bone; action, elevates the larynx; nerve, 

 hypoglossal. 



OMO-HYOID. Origin, from the upper border of the scapula 

 and the transverse ligament; insertion, into the lower border of 

 the os hyoides; its centre is tendinous and bound down to the 

 cartilage of the first rib by a process of the deep cervical fascia ; 

 action, depresses the hyoid bone and draws it backward; nerve, 

 from the communicating loop above. 



SUPRA-HYOID REGION". 



DIGASTRIC. Origin, by two bellies posterior from digas- 

 tric groove of mastoid process of the temporal bone, anterior 



