OF THE BACK 



405 



The First Layer (Fig. 312). 



Trapezius. 



Latissimus dorsi. 



Dissection (Fig. 311). Place the body in a prone position, with the arms extended over 

 the sides of the table, and the thorax and abdomen supported by several blocks, so as to render 

 the muscles tense. Then make an incision along the middle line of the back from the occipital 

 protuberance to the coccyx. Make a transverse incision from the upper end of this to the mas- 

 toid process, and a third incision from its lower end, along the crest of the ilium to about its 

 middle. This large intervening space should, for convenience of dissection, be subdivided by 

 a fourth incision, extending obliquely from the spinous process of the last thoracic vertebra, 

 upward and outward, to the acromion process. This incision corresponds with the lower border 

 of the Trapezius muscle. The flaps of integument are then to be removed in the direction shown 

 in the figure. 



The superficial fascia is exposed upon removing the skin from the back. It 

 forms a layer of considerable thickness and strength, in which a quantity of 

 granular pinkish fat is contained. It is con- 

 tinuous with the superficial fascia in other 

 parts of fhe body. 



The deep fascia is a dense fibrous layer 

 attached to the occipital bone, the spines of 

 the vertebrae, the crest of the ilium, and the 

 spine of the scapula. It covers over the 

 superficial muscles, forming sheaths for them, 

 and in the neck forms the posterior part of the 

 deep cervical fascia; in the thorax it is con- 

 tinuous with the deep fascia of the axilla and 

 thorax, and in the abdomen with that covering 

 the abdominal muscles. In the back of the 

 thoracic region the deep fascia is called the 

 vertebral aponeurosis. It covers the Erector 

 spinae muscles, and is the dorsal layer of the 

 lumbar fascia. 



The Trapezius (m. trapezius) is a broad, flat, 

 triangular muscle, placed immediately beneath 

 the skin and fascia, and covering the upper 

 and back part of the neck and shoulders. It 

 arises from the external occipita) prntiibpranop 

 and the inner jhird of the superior Curved line 

 of the nrfjpi'tfl.l J^onp; from the ligamentum 

 nuchae, the spinous process of the seventh cer- 

 vical, a nd the spinous processes of all the tho r a - 

 cic vertebrae ; and from the corresponding portion 



-js * . ,. JT T^JJ- . . FIG. 311. Dissection of the muscles of 



or the supraspmous ligament, .brom this origin the back, 



the superior fibres proceed downward and out- 

 ward, the inferior ones upward and outward, the middle fibres horizontally, and are 

 inserted, the superior onesjn to the outer third of the posterior border of the plaviHe 



and into the adjacent part of its upper surface. The middle fibres pass into the 



t -' r - - - "" . -.1, i " ' " " 



inner margin oj jhe acromioiLpXQjcess, and into the superior lip ot the posterior 

 border or crest of the spine of the scapula; the inferior fibres converge near the 

 scapula, and terminate in a triangular aponeurosis, which glides over a smooth 

 surface at the inner extremity of the spine, to be hiwrted into a tubercle at the 

 outer- part of this smooth surface. The Trapezius is fleshy in the greater part 

 of its extent, but tendinous at its origin and insertion. At its occipital origin 



