396 



MYOLOGY 



first, second, and third cervical; the Longus colli, by branches from the second to the seventh 

 cervical nerves. 



Actions. The Longus capitis and Rectus capitis anterior are the direct antagonists of the 

 muscles at the back of the neck, serving to restore the head to its natural position after it has 

 been drawn backward. These muscles also flex the head, and from their obliquity, rotate it, 

 so as to turn the face to one or .the other side. The Rectus lateralis, acting on one side, bends 

 the head laterally. The Longus colli flexes and slightly rotates the cervical portion of the vertebral 

 column. 



V. THE LATERAL VERTEBRAL MUSCLES (Fig. 387). 

 The lateral vertebral muscles are: 



Scalenus anterior. Scalenus medius. 



Scalenus posterior. 



The Scalenus anterior (Scalenus anticus) lies deeply at the side of the necl , 

 behind the Sternocleidomastoideus. It arises from the anterior tubercles of the 

 transverse processes of the third, fourth, fifth, and sixth cervical vertebrae, and 

 descending, almost vertically, is inserted by a narrow, flat tendon into the scalene 

 tubercle on the inner border of the first rib, and into the ridge on the upper surface 

 of the rib in front of the subclavian groove. 



The Scalenus medius, the largest and longest of the three Scaleni, arises 

 from the posterior tubercles of the transverse processes of the lower six cervical 

 vertebrae, and descending along the side of the vertebral column, is inserted by a 

 broad attachment into the upper surface of the first rib, between the tubercle 

 and the subclavian groove. 



The Scalenus posterior (Scalenus posticus}, the smallest and most deeply seated 

 of the three Scaleni, arises, by two or three separate tendons, from the posterior 

 tubercles of the transverse processes of the lower two or three cervical vertebrae, 

 and is inserted by a thin tendon into the outer surface of the second rib, behind 

 the attachment of the Serratus anterior. It is occasionally blended with the 

 Scalenus medius. 



Variations. The Scaleni muscles vary considerably in their attachments and in the arrange- 

 ment of their fibers. A slip from the Scalenus anticus may pass behind the subclavian artery. 

 The Scalenus posticus may be absent or extend to the third rib. The Scalenus pleuralis muscle 

 extends from the transverse process of the seventh cervical vertebra to the fascia supporting the 

 dome of the pleura and inner border of first rib. 



Nerves. The Scaleni are supplied by branches from the second to the seventh cervical nerves. 



Actions. When the Scaleni act from above, they elevate the first and second ribs, and are, 

 therefore, inspiratory muscles. Acting from below, they bend the vertebral column to one or 

 other side; if the muscles of both sides act, the vertebral column is slightly flexed. 



THE FASCLffi AND MUSCLES OF THE TEUNK. 



The muscles of the trunk may be arranged in six groups : 

 I. Deep Muscles of the Back. 



II. Suboccipital Muscles. 

 III. Muscles of the Thorax. 



IV. Muscles of the Abdomen. 

 V. Muscles of the Pelvis. 

 VI. Muscles of the Perineum. 



I. THE DEEP MUSCLES OF THE BACK (Fig. 388). 



The deep or intrinsic muscles of the back consist of a complex group of muscles 

 extending from the pelvis to the skull. They are: 



Splenius capitis. Multifidus. 



Splenius cervicis. Rotatores. 



Sacrospinalis. Interspinales. 



Semispinalis. Intertransversarii. 



