356 THE MUSCULATURE 



Actions. — The longus colli serves to bend the neck forward; the supero-lateral portion, when 

 acting on one side only, serves slightly to bend the neck toward that side and to rotate it ; the 

 infero-lateral portion serves especially to prevent hyperextension. The longus capitis bends the 

 head forward; one side acting alone rotates the head toward that side. 



Variations. — There is considerable variation in the number of vertebrae to which the ten- 

 dons of origin and insertion of the longus colli and longus capitis may be attached and in the 

 extent of fusion of the different fasciculi composing them. There may be fusion with the scale- 

 nus anterior. The atlantico-basilaris internus in 4 per cent, of cases extends from the anterior 

 tubercle of the atlas to the base of the skull. 



9. ANTERIOR AND LATERAL INTERTRANSVERSE 



MUSCLES 



(Fig. 352) 



The anterior intertransverse muscles extend successively between the anterior 

 tubercles of the cervical vertebrae. They lie in front of the anterior divisions of 

 the cervical nerves and are supplied by branches from these divisions. They 

 are usually more or less bound up with the insertions of the scalene and pre- 

 vertebral muscles into these tubercles. The muscle between the atlas and epi- 

 stropheus is frequently missing; when present, it passes in front of the lateral 

 articulation between these vertebrae. The rectus capitis anterior (minor) may 

 be considered a continuation of the series. The lowest muscle may extend 

 between the seventh cervical vertebra and the first rib. The lateral intertrans- 

 verse muscles lie immediately behind the ventral divisions of the spinal nerves and 

 lateral to the dorsal divisions and are supplied by branches from the ventral 

 divisions. The rectus capitis laterahs belongs to this series. The rectus capitis 

 anterior (minor) arises from the lateral mass of the atlas and is inserted into 

 the base of the occipital bone. The rectus capitis lateralis runs from the 

 transverse process of the atlas to the lateral part of the occipital. For the 

 posterior intertransverse muscles see p. 417. 



The rectus capitis anterior (minor). — This arises from the upper surface of the lateral mass 

 of the atlas in front of the articular process and partly from the neighbouring transverse proc- 

 ess. From a tendon the fibre-bundles extend in a nearly parallel direction upward and medially 

 to be inserted on the inferior surface of the basilar portion of the occipital bone in front of the 

 condyle Nerve-supply. — From the first (and second) cervical nerves. Action. — The rectus 

 capitis anterior (minor) serve to bend the head forward and, when the muscles on one side 

 only are contracted, to rotate the head toward the same side. 



Relations. — The muscles of this group are closely applied to the vertebral column. Be- 

 tween the fascia covering them and the fascia surrounding the pharynx which lies in front is 

 a region in which merely a slight amount of loose areolar tissue is found. Dorso-medially the 

 longus colli below and the longus capitis above help to bound the space in which the chief ves- 

 sels and nerves extend between the thorax and the head. 



The rectus capitis lateralis (fig. 352). — Origin. — From the upper surface of the transverse 

 process of the atlas. 



Structure and insertion. — The fibre-bundles give rise to a quadrilateral sheet which passes 

 upward to be inserted on the under surface of the pars lateralis of the occipital bone. 



_ Nerve-supply. — The ventral branch of the suboccipital (first cervical) nerve gives twigs 

 to its ventral surface. 



Action. — To flex the head laterally. 



Relations. — In front lie the anterior primary division of the suboccipital nerve and the 

 internal jugular vein. Behind the muscle lie the superior oblique and the longissimus capitis 

 (trachelo-mastoid) muscles and the atlanto-occipital joint. 



10. DEEP MUSCULATURE OF THE SHOULDER GIRDLE 



(Figs. 348, 353, 354, 388) 



To this group belong four muscles which arise in the lateral cervical region 

 during embryonic development anfl become secondarily attached to the vertebral 

 margin of the scapula. ()n(! of these muscles, the band-like levator scapulae 

 (fig. 353), remains in the c(!rvical region. It extends beneath the sterno-cleido- 

 mastoid, the trapezius, and the; intervening fascia from the transverse processes 

 of th(; first four cervical vtTtebne to the medial angle of the scapula. A second, 

 the large, quadrilateral serratus anterior (magnus) (fig. 354), comes to lie beneath 

 the blade of the scapula and wanders with this to the tiioracic region. It arises, 

 in the adult, from the first nine ribs and is inserted into the vertebral margin of 

 the scapula. The flat, quadrangular rhomboideus major and rhomboideus 



