354 



THE MUSCULATURE 



a tendon which sends a fibrous lamina a short distance upward on the outer surface of the muscle. 

 The tendon is inserted into the scalene tubercle on the upper surface of the body of the first rib. 



The scalenus medius.- — This arises usually from the third to the seventh, sometimes from 

 all seven or from merely the last four or five cervical vertebrse. The origin takes place from the 

 posterior part of the lateral border of the transverse processes by means of a slender tendon from 

 each of the upper and directly by a muscular fasciculus from each of the lower vertebrae. The 

 fasciculi become combined into a compact muscle belly which is inserted in a manner similar to 

 the scalenus anterior into the upper surface of the first rib behind the subclavian groove. The 

 insertion usually extends to the second rib. 



The scalenus posterior arises by short tendons from the posterior tubercles of the transverse 

 processes of the fifth and sixth cervical vertebrae. The origin may extend as high as the fourth 

 vertebra, or as low as the seventh. It is inserted by a short tendon into the lateral surface 

 of the second rib. Occasionally it extends to the third rib. 



Fig. 352. — The Deep Ventral Muscles of the Neck. 



Rectus capitis anterior 

 Rectus capitis lateralis 



Longus capitis 



Orgin of the longus 

 capitis 



Rectus capitis la- 

 teralis 

 Rectus capitis 

 anterior 



Intertransversus 

 anterior 



Intertransversus 

 posterior 



Longus colli 



Origin of scalenus 

 anterior 



Scalenus medius 



Scalenus posterior 



Nerve-supply. — The scalenus anterior is innervated by branches from the'fifth, sixth, and 

 seventh cervical nerves; the middle y)y the fourth, fifth, sixth, seventh, and eighth cervical 

 nerves; the posterior by the seventh or eighth nerves. 



Action. — With the thorax fixed the scalene muscles bend the neck to the side and slightly 

 forward and turn it slightly toward the opposite side. With the neck fixed they serve to lift 

 the first two ribs and are of use in enforced inspiration. In quiet inspiration they serve to 

 fix the first two ribs. 



Relations. — The longus colli lies medial to the scalenus anterior. Dorsally the scalene 

 muscles; medially the pharynx, thyreoid gland, and trachea; ventro-laterally the sterno-cleido- 

 mastoid, infra-hyoid, and sul)r'laviiis muscles and the clavicle bound a space filled with dense 

 fatty areolar tissue in whi(,'li are contained tlie subclavian and carotid arteries, the subclavian 

 and internal jugular veins, the vagus, phrenic, and sympathetic nerves, and numerous smaller 

 blood-vessels and nerves. The iriain branches of the lower five cervical nerves pass laterally 

 between the scalenus anterior and medius. The subclavian artery passes behind, the sub- 

 clavian vein in front, of the attachment of the scalenus anterior. The scalenus medius above 

 and the scalenus posterior below enter into relations dorsally with the levator scapula; and the 

 intrin.sic dorsal musculature, from wliich tliev are separated by fascial septa. 



