432 MYOLOGY 



I. THE MUSCLES CONNECTING THE UPPER EXTREMITY TO THE 

 VERTEBRAL COLUMN. 



The muscles of this group are : 



Trapezius. Rhomboideus major. 



Latissimus dorsi. Rhomboideus minor. 



Levator scapulae. 



Superficial Fascia. The superficial fascia of the back forms a layer of con- 

 siderable thickness and strength, and contains a quantity of granular fat. It is 

 continuous with the general superficial fascia. 



Deep Fascia. The deep fascia is a dense fibrous layer, attached above to the 

 superior nuchal line of the occipital bone; in the middle line it is attached to the 

 ligamentum nuchae and supraspinal ligament, and to the spinous processes of all 

 the vertebrae below the seventh cervical ; laterally, in the neck it is continuous with 

 the deep cervical fascia; over the shoulder it is attached to the spine of the scapula 

 and to the acromion, and is continued downward over the Deltoideus to the arm ; 

 on the thorax it is continuous with the deep fascia of the axilla and chest, and on 

 the abdomen with that covering the abdominal muscles; below, it is attached to 

 the crest of the ilium. 



The Trapezius (Fig. 409) is a flat, triangular muscle, covering the upper and 

 back part of the neck and shoulders. It arises from the external occipital protu- 

 berance and the medial third of the superior nuchal line of the occipital bone, from 

 the ligamentum nuchse, the spinous process of the seventh cervical, and the spinous 

 processes of all the thoracic vertebrae, and from the corresponding portion of the 

 supraspinal ligament. From this origin, the superior fibers proceed downward 

 and lateralward, the inferior upw y ard and lateralward, and the middle horizontally; 

 the superior fibers are inserted into the posterior border of the lateral third of the 

 clavicle ; the middle fibers into the medial margin of the acromion, and into the supe- 

 rior lip of the posterior border of the spine of the scapula; the inferior fibers con- 

 verge near the scapula, and end in an aponeurosis, which glides over the smooth 

 triangular surface on the medial end of the spine, to be inserted into a tubercle 

 at the apex of this smooth triangular surface. At its occipital origin, the Trapezius 

 is connected to the bone by a thin fibrous lamina, firmly adherent to the skin. 

 At the middle it is connected to the spinous processes by a broad semi-elliptical 

 aponeurosis, which reaches from the sixth cervical to the third thoracic vertebrae, 

 and forms, with that of the opposite muscle, a tendinous ellipse. The rest of the 

 muscle arises by numerous short tendinous fibers. The two Trapezius muscles 

 together resemble a trapezium, or diamond-shaped quadrangle: two angles corre- 

 sponding to the shoulders; a third to the occipital protuberance; and the fourth 

 to the spinous process of the twelfth thoracic vertebra. 



Variations. The attachments to the dorsal vertebrae are often reduced and the lower ones are 

 often wanting; the occipital attachment is often wanting; separation between cervical and dorsal 

 portions is frequent. Extensive deficiencies and complete absence occur. 



The clavicular insertion of this muscle varies in extent; it sometimes reaches 

 as far as the middle of the clavicle, and occasionally may blend with the posterior 

 edge of the Sternocleidomastoideus, or overlap it. 



The Latissimus dorsi (Fig. 409) is a triangular, flat muscle, which covers the 

 lumbar region and the lower half of the thoracic region, and is gradually con- 

 tracted into a narrow fasciculus at its insertion into the humerus. It arises by 

 tendinous fibers from the spinous processes of the lower six thoracic vertebrae 

 and from the posterior layer of the lumbodorsal fascia (see page 397), by which 

 it is attached to the spines of the lumbar and sacral vertebrae, to the supraspinal 

 ligament, and to the posterior part of the crest of the ilium. It also arises by 



