DISSECTION OF THE HEAD AND NECK. 159 



mentum nuchse, as far as the 2iid or 3rd cervical vertebra, where its 

 terminal branches anastomose with those of the occipito-muscular and 

 dorsal arteries. 



Veins. The dorsal and superior cervical arteries are accompanied 

 by veins of the same names, which, after entering the chest, dischai-ge 

 themselves into the anterior vena cava. 



Directions. — The complexus, splenius, and trachelo-mastoideus muscles 

 may now be removed as far as the hinder end of the axis. This will 

 expose the semispinalis colli muscle and the ligamentum nuchas. 



The Semispinalis Colli Muscle (Fig. 19) rests on the laminae of 

 the cervical vertebrae, and consists of five bundles. The most posterior 

 of these bundles may be described as taking origin from the anterior 

 articular process of the 7th cervical vertebra, and passing forwards 

 and inwards to be inserted into the superior spine of the 6th vertebra. 

 The most anterior bundle passes in the same way between the 3rd 

 vertebra and the axis, while the intermediate bundles have corresponding 

 attachments. 



Action. — The right and left muscles, acting in concert, will extend 

 (elevate) the cervical part of the spinal column. The muscle of one 

 side, acting singly, will rotate and incline the spinal column to the 

 opposite side. 



The Intbrteansvbrsales Colli Muscles (Fig. 20). These form a 

 set of six mnscular bundles with strong tendinous intersections, and 

 cover the sides of the cervical vertebrae. There is one bundle for each 

 intervertebral articulation except the first. Each muscular bundle 

 consists of an upper and a lower slip ; and it may be described as arising 

 from the articular process of one vertebra, and passing forwards to be 

 inserted into the transverse process of the vertebra in front. The 

 muscles conceal the intervertebral foramina and the vertebral vessels ; 

 and they are perforated by bi-anches of these vessels, and by the superior 

 and inferior primary branches of the spinal nerves of the neck. 



Action. — To bend the neck laterally. 



The Rectus Capitis Anticus Major (Plate 28 and Fig. 20). This 

 muscle begins by a tapering point on the side of the vertebral column 

 at the 5th cervical vertebra ; and, passing forwards and inwards, it gains 

 the inferior face of the atlas, in passing to the base of the skull. It 

 arises from the transverse processes of the 5th, 4th, and 3rd vertebrae, 

 the slip of origin from the first of these crossing the point of the 

 scalenus. Its insertion, which is not to be exposed at present, is into 

 the tubercular processes at the junction of the basilar process of the 

 occipital bone with the body of the sphenoid. 



Action. The right and left muscles, acting together, flex the head. 



When only one muscle acts it inclines the head to the same side. 



The Scalenus (Plate 3 and Fig. 20). This muscle is situated on the 



