THE BACK. 



395 



MUSCLES OF THE BACK, GROUPED ACCORDING TO LAYERS, AND THEIR NERVE-SUPPLY. 



First layer, . . 

 Second layer, . 



Third layer, . 

 Fourth layer, . 



K 



c 



t/i 

 Fifth layer, . >_ 



o 

 G 



W 



Sixth layer, . . 

 Seventh laver, 



Trapezius. Nerve-supply, spinal accessory, cervical plexus. 



Levator anguli scapulae. Nerve-supply, cervical plexus. 



Rhomboideus minor. Nerve-supply, brachial plexus. 



Rhomboideus major. Nerve-supply, brachial plexus. 



Latissimus dorsi. Nerve-supply, the long subscapular. 



Serratus posticus superior. 1 Nerve-supply, posterior divisions of spinals, 



Serratus posticus inferior, j external branches. 



Splenius capitis. ) Nerve-supply, posterior divisions of spinals, external 



Splenius colli. } branches. 



Outer division (nerve-supply, all by posterior divisions, spinal nerves) : 



1. Ileo-costalis. 



2. Musculus accessorius ad ileo-costalem. 



3. Musculus cervicalis ascendens. 



Middle division (nerve-supply, posterior divisions of spinals) : 



1. Musculus longissimus dorsi. 



2. Musculus transversalis colli. 



3. Musculus trachelo-mastoideus. 



Inner division (nerve-supply, posterior divisions of spinals) : 



Musculus spinalis dorsi. 

 Musculus complexus. Nerve-supply, suboccipital, great occipital, posterior 



division. 



Semispinalis colli. Nerve-supply, posterior divisions of spinal. 

 Semispinalis dorsi. Nerve-supply, posterior divisions of spinal. 

 Rotatores spinae. Nerve-supply, posterior divisions of spinal. 

 Multifidus spinae. Nerve-supply, posterior divisions of spinal. 



Interspinales. Nerve-supply, posterior divisions of spinal. 

 Intertransversales. Nerve-supply, posterior divisions of spinal. 



Occipital Group (nerve-supply, suboccipital nerve). Rectus capitis posticus 

 minor, rectus capitis posticus major, rectus capitis lateralis, obliquus superior, 

 obliquus inferior. Nerve-supply, great occipital and suboccipital nerves. 



ANALYSIS OF THE SIMPLE MOVEMENTS OE THE SPINAL 

 COLUMN AND THE MUSCLES WHICH PRODUCE THEM. 



View the skeleton from behind, and note the juxtaposition of spines, laminae, 

 transverse processes, articular processes, and bodies or centra of vertebrae. Note 

 the head of the rib articulating with the body, and the tubercle of the rib articulat- 

 ing with the transverse process of a vertebra. (Fig. 276.) Each is a movable 

 articulation, because it has a synovial sac. Note the central pulpy nature of the 

 intervertebral disc. Note the manner in which the head of the rib articulates 

 with two bodies and the cartilaginous disc, and recall the exceptions to this rule 

 in the first, ninth, tenth, eleventh, and twelfth thoracic vertebrae. (Fig. 277.) 



SIMPLE MOVEMENTS OF THE SPINE. 



1. Lateral flexion of the column by the intertransversales. 



2. Extension of the column by the interspinalcs and spinalis dorsi. 



3. Lateral rotation by the rotatores spinae, extending from the transverse pro- 

 cess of the vertebra below to the lamina of the bone above. 



4. Extension and lateral rotation of the column by the multifidus spinae, in a 

 typical region extending from the transverse processes of the vertebrae below, to 

 the lower border of the spines above, from the last lumbar to the second 

 cervical vertebrae. 



Note that extension and lateral rotation are the two most common move- 



