562 



NECK. 



passes from the upper edge of the trans- 

 verse process of the atlas to the transverse or 

 jugular process of the occiput: the latter, on 

 a plane anterior to this, from the anterior root 

 of the transverse process and side of the an- 

 terior arch, inclines upward and alittle inward, 

 to be inserted into the basilar process of the 

 occipital bone behind the rectus capitis anticus 

 major, between its outer edge and the foramen 

 magnum. The rectus capitis lateralis separates 

 the vertebral artery from the jugular vein. 



These muscles in approximating their points 

 of attachment can give lateral flexion to the 

 neck and to the head. 



The scaleni ( Costo-trachelien : Chauss.^) are 

 situated at the lower lateral part of the neck, 

 extending from the transverse processes to the 

 first two ribs, and are of triangular form. 

 They have been variously described by different 

 anatomists, some considering their fleshy mass 

 as a single muscle, others distinguishing in it 

 two, three, and even five parts. I shall adopt 

 the more usual modern division, which recog- 

 nises two muscles, scalenus anticus and scalenus 

 posticus. 



Scalenus anticus arises from the third, fourth, 

 and fifth cervical vertebrae, at the anterior tuber- 

 cles and notched extremities of their transverse 

 processes, by slips of tendon, to which muscular 

 fibres directly succeed, and descends with an 

 inclination outward and forward to be inserted 

 by a flat strong tendon into a roughness about 

 the middle of the anterior third of the first rib. 

 This insertion is important as affording a guide 

 to the position of the subclavian artery, which, 

 in arching over the rib, lies behind this tendon 

 and separates it from the insertion of the 

 scalenus posticus. It is triangular in shape 

 and fleshy in nearly its whole extent : externally 

 it presents a free border, from behind which 

 emerge the elements of the brachial plexus 

 and the subclavian artery ; internally its origin 

 adjoins that of the rectus capitis anticus major, 

 from which it is demarked by the arteria cervi- 

 calis ascendens, and toward its insertion is 

 separated from the longus colli by a space in 

 which the vertebral artery ascends ; its anterior 

 surface is crossed from above by the phrenic 

 nerve, and transversely by branches of the 

 thyroid axis; its deep surface is separated from 

 the scalenus posticus by the emerging trunks 

 of the nerves, and the space between them, 

 broadening towards the first rib, includes there 

 the brachial plexus and subclavian artery the 

 latter being below and in front of the former, 

 and in immediate contact with the rib. 



Scalenus posticus, larger than the preceding, 

 behind which it is situated, arises by six ten- 

 dons, to which muscular fibres directly succeed, 

 from the posterior tubercles of the transverse 

 processes of the six last cervical vertebra. The 

 first slip (often partly derived from the atlas) 

 is joined, as it descends, by the others in suc- 

 cession, and a large triangular muscle results, 

 which has its base at the transverse processes 

 and its apex at the second rib. It is inserted, 

 first, by an anterior broad slip into the outer 

 edge of the first rib, from the tubercle behind 

 as far forward as the arterial impression in 



front ; secondly, by a smaller slip, which is 

 prolonged from the posterior surface of the 

 muscle to the upper edge of the second rib 

 near its tuberosity. This muscle corresponds 

 anteriorly to the scalenus anticus, from which 

 it is separated by the brachial plexus and sub- 

 clavian artery; posteriorly to the levator anguli 

 scapulae ; by its inner edge to its points of 

 origin; by its outer edge to the serratus magnus 

 and transversalis colli artery, to branches of the 

 cervical and brachial plexus of nerves, and to 

 the sterno-mastoid muscle ; lastly, by its in- 

 ferior-internal edge to the longus colli, from 

 which it is divided by the anterior branch of 

 the first dorsal nerve, and by the (generally) 

 common trunk of the deep cervical and first 

 intercostal arteries. 



The action of the scaleni, as of the muscles 

 previously described, consists rather in main- 

 taining steadiness and resisting lateralisation of 

 the neck, than in effecting any considerable 

 movement. They may, however, in a slight 

 degree, bend the neck laterally. The vertebrae 

 being fixed, their muscles by acting together 

 may elevate the first two ribs and so assist in 

 inspiration. The scaleuus anticus can, from 

 its advanced insertion, act more effectually 

 thus. This action is illustrated in all deeper 

 inspirations ; for these differ from ordinary 

 breathing therein, that the chest is expanded 

 by the elevation of the ribs and sternum, in its 

 antero-posterior and transverse diameters, in 

 addition to the ordinary increase of capacity 

 which it gains by the descent of the dia- 

 phragm; and, in order to the effective action 

 of the intercostals, the first rib must be ren- 

 dered immoveable. The scaleni, in raising the 

 anterior extremity of the first ribs, favour the 

 advance of the sternum, and then rigidly fixing 

 these bones enable the intercostal muscles to 

 give to the ribs beneath that slight axial rota- 

 tion by which the transverse diameter of the 

 chest is increased.* 



The intrinsic muscles of the larynx having 

 already been described (see LARYNX), and 

 those of the pharynx being for future descrip- 

 tion (see PHARYNX), our second class will com- 

 prise only the muscles of the os hyoides and 

 tongue, viz. depressors of the os hoides, the 

 sterno-hyoid,omo-hi/oid,a.nd sterno-tliyroid, with 

 its continuation the thyro-hyoid; its elevators, 

 the digastric, stylo-hyoid, mylo-hyoid, genio- 

 hi/oid ; muscles of the tongue, hyo-glossus t 

 genio- hyo-glossus, and lingua/is 



The sterno-hyoid and sterno-tliyroid are two 

 riband-like muscles, having respectively the 

 attachments denoted by their names, situated 

 beside the median line, so as to be divided 



* Within the last year I have observed in two 

 subjects an importantly anomalous insertion of the 

 scalenus anticus. Its main bulk of tendon passed 

 on both sides to an insertion behind the artery, a 

 very small slip only taking ihe usual course. The 

 strong flat tendon, which is usually so trustworthy 

 a guide to the artery, would in these cases have in- 

 volved an operator in the misfortune of surrounding 

 the nerves with his ligature ; and the circumstance 

 illustrates the necessity of trying the effect of tem- 

 porary pressure on a supposed arterial trunk, before 

 conclusively tightening the ligature around it. 



