THE UPPER LI2JB 



293 



at either extremity, from which circumstance this part is known 

 as the biventer cervicis. About the level of the axis the muscle 

 usually presents another faint transverse intersection. 



Nerve-supply. — (i) The posterior primary division of the first 

 cervical or suboccipital nerve ; (2) the great occipital ; and (3) the 

 posterior primary divisions of cervical nerves below the second. 



The innermost and longest fibres pass almost vertically upwards. 



.Trachelo-mastoid 



V- Tracbelo-niastoid 



TransTCTsalis Cervicis 



Semi^Nnalls Colli 



Semispinal is Dorsi. 



- ^\^ S^ ^\;\.f:^^-^\0, Longissimus Doisi 



(turned outn-ards) 



Fig. 170. — The Middle Column of the Erector Spin^, and the 

 Semispinales Muscles. 



whilst the outer and upper fibres, which are short, pass upwards 

 and inwards. 



Action. — To extend the head ind incline it to one side, the face 

 being turned to the opposite side. 



A small part of the complexus may appear superficially in the 

 upper part of the posterior triangle of the neck, this portion being 

 pierced by the great occipital nerv^e. As high as the axis spine the 

 muscle rests upon the semispinalis colh, and in this situation an 

 arterial anastomosis takes place between the deep cervical of the 

 superior intercostal from the second part of the subclavian and the 



