THE NECK 



1357 



border of the clavicular origin must be remembered in such operations as tenotomy here. These 

 veins vary in size inversely to each other; the anterior jugulars are joined by numerous trans- 

 vesre branches and become larger below. They have no valves. 



Of the chief arteries to the sterno-mastoid, that from the superior thyreoid will be divided 

 in gature of the common carotid; that from the occipital runs with the spinal accessory nerve. 



Behind the stemo-clavicular joint lies the commencement of the innominate 

 veins, the bifurcation of the innominate artery on the right, and the common 

 carotid artery on the left; deeper still lie the pleura and lung. 



The clavicle. — This bone can be felt beneath the skin in its whole length. 

 It forms the only bony connection between the upper limbs and the trunk. As 

 one traces it laterall^^ toward the acromial end, it rises somewhat, particularly 

 in children and in subjects of good muscular development. The skin over it is 

 thin but very mobile, and consequently is not often wounded. The most im- 

 portant posterior relations of this bone are, passing from the medial end laterally, 

 the subclavian vein, the subclavian artery, and the cords of the brachial plexus 

 as they lie on the first rib. 



Fig. 1101. — Anterior and Lateral Cervical Muscles. 



Stylo-glossus 

 Hyo-glossus 



Mylo-hyoid 



Anterior belly of 

 digastric 

 Raphe of mylo- 

 hyoid 



Inferior constrictor 

 Anterior belly of omo- 

 hyoid 



Sterno-hyoid 

 Sterno-thyreoid 



Thyreo-hyoid 



Stylo-hyoid 



Posterior belly of 

 digastric 



Splenius capitis 



Sterno-mastoid 

 Levator scapulae 



Scalenus medius 

 Trapezius 



Scalenus posterior 



Posterior belly of 

 omo-hyoid 



The vein occupies the angle between the first rib and the clavicle, and hence is, as a rule, 

 the first structure compressed in growths of this bone. The artery lies on a deeper plane be- 

 hind the mid-point of the clavicle, and the nerve cords extend a little further laterally. The 

 subclavius muscle forms a protective cushion between the bone and these important structures, 

 and this accounts for the rarity of injury to them in fracture of the clavicle. Behind the medial 

 half of the clavicle the apex of the lung extends upward into the neck to a height of 2.5-3.7 cm. 

 (1-1^ in.), and consequently is liable to be wounded by a stab in the root of the neck. 



Cervical triangles. — In front of the sterno-mastoid is the anterior triangle, 

 which is subdivided into three smaller triangles by the cUgastric muscle above, 

 and the anterior belly of the omo-hyoid below (fig. 1101). These smaller tri- 

 angles are called, from above, the submaxillary, the superior and inferior carotid 

 triangles. 



The submaxillary or digastric triangle is bounded above by the jaw, and a line 

 drawn back to the mastoid process; below, by the digastric and stylo-hj'oid 

 muscles; and in front by the middle line of the neck. 



