INFRA-HYOID REGION. 



257 



muscle is separated, below, from its fellow by a considerable interval ; but they 

 approach one another in the middle of their course, and again diverge as they 

 ascend. It often presents, immediately above its origin, a transverse tendinous 

 intersection, analogous to those in the Kectus abdominis. 



Variations. This mnscle sometimes arises from the inner extremity of the clavicle, and the 

 posterior sterno-clavicular ligament, or from the sternum and this ligament ; from either bone 

 alone, or from all these parts ; and occasionally has a fasciculus connected with the cartilage of 

 the first rib. 



delations. By its superficial surface, below, with the sternum, sternal end of 

 the clavicle, and the Sterno-mastoid ; and above, with the Platysma and deep 

 cervical fascia. By its deep surface, with the Sterno-thyroid, Crico-thyroid, and 

 Thyro-hyoid muscles, the thyroid gland, the superior thyroid vessels, the 

 crico-thyroid and thyro-hyoid membranes. 



Fig. 154. Muscles of the Neck. Anterior View. 



The Slerno-lliyroid is situated beneath the preceding muscle, but is shorter 

 and wider. It arises from the posterior surface of the first bone of the 

 sternum, below the origin of the Sterno-hyoid, and occasionally from the edge of 

 the cartilage of the first rib, and is inserted into the oblique line on the side 

 of the ala of the thyroid cartilage. This muscle is in close contact with its 

 fellow at the lower part of the neck ; and is frequently traversed by a trans- 

 verse or oblique tendinous intersection, analogous to those in the Eectus 

 abdominis. 



Variations. This muscle is sometimes continuous with the Thyro-hyoid and Inferior con- 

 strictor of the pharynx ; and a lateral prolongation from it sometimes passes as far as the os 

 hyoides. 



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