MUSCLES OF THE BACK. 269 



MUSCLES AND FASCIAE OF THE TEUNK. 



The Muscles of the Trunk may be subdivided into four groups : 



1. Muscles of the Back. 3. Muscles of the Thorax. 



2. Muscles of the Abdomen. 4. Muscles of the Perineum. 



MUSCLES OF THE BACK. 



The Muscles of the Back are very numerous, and may be subdivided into five 

 layers : 



FIRST LAYER. . 1 



Cervical region. 



Trapezius. 



Latissimus dorsi. Cervicalis ascendens. 



Transversahs coin. 



SECOND LAYER. Trachelo-mastoid. 



Levator anguli scapula Complexus. 



Ehomboideus minor. ^venter cervicis. 



Ehomboideus major. Spmalis cervicis. 



THIRD LAYER. 



Serratus posticus superior. FIFTH LAYER. 



Serratus posticus inferior. 



Splenius capitis. Semi-spinalis dorsi. 



Splenius colli. Semi-spinalis colli. 



FOURTH LAYER. Multifidus spin*. 



Eotatores spinse. 



Sacral and lumbar regions. Supra-spinales. 



Erector spinsB. Inter-spinales. 



Extensor coccygis. ' 



Dorsal region. Inter-transversales. 



Sacro-lumbalis. Eectus posticus major. 



Musculus accessorius ad sacro-lumbalem. Eectus posticus minor. 

 Longissimus dorsi. Obliquus superior. 



Spinalis dorsi. Obliquus inferior. 



FIRST LAYER. 

 Trapezius. Latissimus Dorsi. 



Dissection (fig. 159). The body should be placed in the prone position, with the arms ex- 

 tended over the sides of the table, and the chest and abdomen supported by several blocks, so 

 as to render the muscles tense. An incision should then be made along the middle line of the 

 back, from the occipital protuberance to the coccyx. From the upper end of this, a transverse 

 incision should extend to the mastoid process ; and from the lower end, a third incision should 

 be made along the crest of the ilium to about its middle. This large intervening space, for con- 

 venience of dissection, should be subdivided by a fourth incision, extending obliquely from the 

 sninous process of the last dorsal vertebra, upwards and outwards, to the acromion process. 

 This incision corresponds with the lower border of the Trapezius muscle. The flaps of integu- 

 ment should then be removed in the direction shown in the figure in the next page. 



The Trapezius is a broad, flat, triangular muscle, placed immediately beneath 

 the skin, and covering the upper and back part of the neck and shoulders. It 

 arises from the inner third of the superior curved line of the occipital bone ; from the 

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

 dorsal vertebra? ; and from the corresponding portion of the supra-spinous ligament. 

 From this origin, the superior fibres proceed downwards and outwards ; the inferior 

 ones, upwards and outwards ; and the middle fibres, horizontally ; and are inserted, 

 the superior ones, into the outer third of the posterior border of the clavicle ; the 

 middle fibres, into the upper margin of the acromion process, and into the whole 



