200 THE MUSCLES. 



10. Scalenus. (Figs. 104, 105, 106.) 

 Synonyms. — Costo-traoheleus — Girard. {Scalenus anticus and posticus of Man.) 



Situation— Direction — Composition.— Deeply situated at the inferior 

 part of the neck, in an oblique direction downwards and backwards, this 

 muscle comprises two portions of unequal dimensions, placed one above 

 another. 



Form — Structure — Attachments. — A. The superior portion {scalenus posti- 

 cus of Man), the smallest, is composed of three or four fleshy fasciculi, attached 

 by their extremities to the transverse processes of the last three or four 

 cervical vertebree. The last terminates at the superior extremity of the 

 first rib. 



B. The inferior {scalenus anticus of Man), the most considerable, is 

 flattened on both sides, thick and wide posteriorly, thin and narrow 

 anteriorly, and is composed almost entirely of fleshy fibres which are longest 

 as they are inferior. It is attached : 1 , To the transverse processes of the 

 last four cervical vertebras by short fasciculi scarcely distinct from one 

 another, the first of wliich is crossed by the last digitation of the great 

 anterior straight muscle ; 2, To the anterior border and external face of the 

 first rib, where all its fibres end. 



Relations. — The scalenus responds : by its external face, to the sub- 

 scapulo-hyoideus, mastoido-humeralis, and the sterno-presoapularis ; by its 

 internal face, to the longus colli, trachea, common carotid artery and its 

 accompanying nerves, and — ^on the left side only — to the oesophagus ; by its 

 inferior border, to the jugular vein. The two portions of the scalenus are 

 separated from one another, in front of the first rib, by an interspace 

 traversed by the nerves of the brachial plexus. 



Action. — When the first rib is the fixed point, this muscle either directly 

 flexes the neclc or inclines it to one side. When the neck is the fixed point, 

 it draws forward the first rib and fixes it in this position during the 

 dilatation of the chest, in order to aid the inspiratory action of the external 

 intercostal muscles. * 



11. Long Muscle of the Nech. 



Synonyms.— Fle-aoT longus colli— Bourgelat. Subdorso-atloideua— GirartJ. (^Longus 

 colli^Percivall. Dorso-athideus — Leyh.) 



i Situation — Composition. — A single and considerable muscle, immediately 

 covering the inferior aspect of all the cervical and the first six dorsal 

 vertebree, and composed of two lateral portions which are united on the 

 median line, and constitute, in certain animals, two distinct muscles. 



Structure — Attachments. — Each lateral portion of the longus colli is 

 composed of a succession of very tendinous fasciculi. The most^posterior of 

 these is attached to the inferior face of the bodies of the first six dorsal 

 vertebrae, and proceeds directly forward to reach the inferior tubercle of the 

 sixth cervical vertebra, into which it is inserted by a strong tendon. The 

 other fasciculi, less considerable, and confounded outwardly with the inter- 

 transversales of the neck, are carried from one cervical vertebra to another, 

 and are directed forwards, upwards, and inwards, in converging towards those 

 of the opposite side. They are attached successively : outwardly, to the 

 transverse processes of the last six cervical vertebrae; inwardly, to the 

 inferior ridge on the bodies of the first six. The most anterior fasciculus 

 passes to the inferior tubercle of the atlas, into which it is inserted by a 



