STERNO-HYOIDEUS. OMO-HVOIDEUS. 183 



deep fascia from off the front of the neck between the two sterno- 

 raastoid muscles. The omo-hyoid to be seen in its whole extent re- 

 quires that the sterno-mastoid muscle should be divided from its origin 

 and turned aside. 



The STERNO-HYOIDEUS, is a narrow riband-like muscle, arising 

 from the posterior surface of the first bone of the sternum and inner 

 extremity of the clavicle. It is inserted into the lower border and 

 posterior surface of the body of the os hyoides. The sterno-hyoidei 

 are separated by a considerable interval at the root of the neck, but 

 approach each other as they ascend : they are frequently traversed by 

 a tendinous intersection. 



Relations. By its external surface with the deep cervical fascia, the 

 platysma myoides and sterno-mastoid muscle ; by its internal surface 

 with the sterno-thyroid, and thyro-hyoid muscle, and the superior 

 thyroid artery. 



The STERNO-THYROIDEUS, broader than the preceding beneath 

 which it lies, arises from the posterior surface of the upper bone of 

 the sternum, and from the cartilage of the first rib ; it is inserted 

 into the oblique line on the great ala of the thyroid cartilage. The 

 inner borders of these muscles lie in contact along the middle line, 

 and they are generally marked by a tendinous intersection at their 

 lower part. 



Relations. By its external surface with the sterno-hyoid, omo- 

 hyoid, and sterno-mastoid muscle ; by its internal surface, with the 

 trachea and inferior thyroid veins, with the thyroid gland, the lower 

 part of the larynx, the sheath of the common carotid artery and 

 internal jugular vein, with the subclavian vein and vena innominata, 

 and on the right side with the arteria innominata. The middle thy- 

 roid vein lies along its inner border. 



The THYRO-HYOIDEUS is the continuation upwards of the sterno- 

 thyroid muscle. It arises from the oblique line on the thyroid carti- 

 lage, and is inserted into the lower border of the body and great cornu 

 of the os hyoides. 



Relations. By its external surface with the sterno-hyoid and omo- 

 hyoid muscle ; by its internal surface with the great ala of the thyroid 

 cartilage, the thyro-hyoidean membrane, and the superior laryngeal 

 artery and nerve. 



The OMO-HYOIDEUS (UIMS, shoulder) is a double-bellied muscle 

 passing obliquely across the neck from the scapula to the os hyoides ; 

 it forms an obtuse angle behind the sterno-mastoid muscle, and is 

 retained in that position by means of a process of the deep cervical 

 fascia which is connected to the inner border of its tendon. It arises 

 from the upper border of the scapula, and from the transverse liga- 

 ment of the supra- scapular notch, and is inserted into the lower border 

 of the body of the os hyoides. 



Relations. By its superficial surface with the trapezius, the sub- 

 clavius and clavicle, the deep cervical fascia and platysma myoides, 

 the sterno-mastoid, and the integument. By its deep surface with the 



