THE LATERAL VERTEBRAL REGION. 425 



obliquely upward and inward, is inserted into the basilar process immediately 

 behind the preceding muscle. 



Relations. By its anterior surface, with the Rectus capitis anticus major; by 

 its posterior surface, with the front of the occipito-atlantal articulation. 



The Rectus capitis lateralis is a short, flat muscle, which arises from the upper 

 surface of the transverse process of the atlas, and is inserted into the under surface 

 of the jugular process of the occipital bone. 



Relations. By its anterior surface, with the internal jugular vein ; by its pos- 

 terior surface, with the vertebral artery. On its outer side lies the occipital artery ; 

 on its inner side, the suboccipital nerve. 



The Longus colli is a long, flat muscle, situated on the anterior surface of the 

 spine, between the atlas and the third dorsal vertebra. It is broad in the middle, 

 narrow and pointed at each extremity, and consists of three portions : a superior, 

 oblique, an inferior oblique, and a vertical portion. The superior oblique portion 

 arises from the anterior tubercles of the transverse processes of the third, fourth, 

 and fifth cervical vertebrae, and, ascending obliquely inward, is inserted by a nar- 

 row tendon into the tubercle on the anterior arch of the atlas. The inferior 

 oblique portion, the smallest part of the muscle, arises from the front of the bodies 

 of the first two or three dorsal vertebrae, and, ascending obliquely outward, is 

 inserted into the anterior tubercles of the transverse processes of the fifth and 

 sixth cervical vertebrae. The vertical portion lies directly on the front of the spine ; 

 it arises, below, from the front of the bodies of the upper three dorsal and lower 

 three cervical vertebrae, and is inserted above into the front of the bodies of the 

 second, third, and fourth cervical vertebrae above. 



Relations. By its anterior surface, with the pharynx, the oesophagus, sympa- 

 thetic nerve, the sheath of the great vessels of the neck, the inferior thyroid artery, 

 and recurrent laryngeal nerve ; by its posterior surface, with the cervical and dorsal 

 portions of the spine. Its inner border is separated from the opposite muscle by 

 a considerable interval below, but they approach each other above. 



8. Lateral Vertebral Region. 



Scalenus anticus. Scalenus medius. 



Scalenus posticus. 



The Scalenus anticus is a conical-shaped muscle, situated deeply at the side of 

 the neck, behind the Sterno-mastoid. 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 impression 

 on the inner border and upper surface of the first rib. The lower part of this 

 muscle separates the subclavian artery and vein, the latter being in front, and the 

 former, with the brachial plexus, behind. 



Relations. In front, with the clavicle, the Subclavius, Sterno-mastoid, and 

 Omo-hyoid muscles, the transversalis colli, the suprascapular and ascending cer- 

 vical arteries, the subclavian vein, and the phrenic nerve ; by its posterior surface, 

 with the Scalenus medius, pleura, the subclavian artery, and brachial plexus of 

 nerves. It is separated from the Longus colli, on the inner side, by the vertebral 

 artery. On the anterior tubercles of the transverse processes of the cervical ver- 

 tebrae, between the attachments of the Scalenus anticus and Longus colli, lies the 

 ascending cervical branch of the inferior thyroid artery. 



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, behind the groove for the sub- 

 clavian artery, as far back as the tubercle. It is separated from the Scalenus 

 anticus by a subclavian artery below and the cervical nerves above. The pos- 

 terior thoracic, or nerve of Bell, is formed in the substance of the Scalenus medius 

 and emerges from it. 



