SUPERFICIAL CERVICAL REGION. 



255 



and thinner at each extremity. It arises, bj two heads, from the sternum and 

 clavicle. The sternal portion arises by a rounded fasciculus, tendinous in front, 

 fleshy behind, from the upper and anterior part of the first piece of the sternum, 

 and is directed upwards and backwards. The clavicular portion arises from the 

 inner third of the superior border of the clavicle, being composed of fleshy and 

 aponeurotic fibres ; it is directed almost vertically upwards. These two portions 

 are separated from one another, at their origin, oy a triangular cellular interval ; 

 but become gradually blended, below the middle of the neck, into a thick rounded 

 muscle, which is inserted, by a strong tendon, into the outer surface of the mastoid 

 process, from the apex to its superior border, and by a thin aponeurosis into the 

 outer two-thirds of the superior curved line of the occipital bone. This muscle 

 varies much in its extent of attachment to the clavicle ; in one case it may be as 

 narrow as the sternal portion, in another as much as three inches in breadth. 



Fig. 153. Muscles of the Neck, and Boundaries of the Triangles. 



When the clavicular origin is broad, it is occasionally subdivided into numerous 

 slips, separated by narrow intervals. More rarely, the corresponding margins of 

 the Sterno-mastoid and Trapezius have been found in contact. In the application 

 of a ligature to the third part of the subclavian artery, it will be necessary, where 

 the muscles have an arrangement similar to that above-mentioned, to divide a 

 portion of one or of both, in order to facilitate the operation. 



This muscle divides the quadrilateral space at the side of the neck into two 

 triangles, an anterior and a posterior. The boundaries of the anterior triangle 

 being, in front, the median line of the neck; above, the lower border of the bodv 

 of the jaw, and an imaginary line drawn from the angle of the jaw to the mastoid 



