1102 SURGICAL AND TOPOGRAPHICAL A^ATOMY 



The superior carotid triangle is Ixjundecl above by the di^rastiic, Vjelow by 

 the omu-hyoi(K and behind l)y tlie sterno-niastuid. It contains tlie upper part of 

 the common carotid and its branches, the external being somewhat anterior to the 

 internal. All the branches of the external carotid, save the three just given, are 

 found in this space,- together with their veins, the internal jugular vein, the vagus 

 and symi)athetic nerves, and, for a short distance, the spinal accessory, together 

 with those nerves which lie in front of and behind the carotids. 



The inferior carotid or tracheal triangle is bounded above by the omo-hyoid, 

 behind by the sterno-mastoid, and in front ])y the middle line of the neck. It 

 contains the lower part of the carotid sheath and its contents, with, behind it, the 

 inferior laryngeal nerve and inferior thyroid vessels, and to the inner side the 

 trachea and thyroid gland. 



The position of the branches of the external carotid should be remembered. 

 The superior thyroid, arising just below the level of the great cornu of the hyoid 

 bone, passes downwards and forwards to the back part of the thyroid cartilage and 

 upper part of the thyroid body. Many of its branches are important in surgery. 

 The superior laryngeal perforates the thyro-hyoid membrane. The sterno- 

 mastoid passes outwards into the middle of the muscle, across the carotid sheath. 

 The crico-thyroid crosses the space of the same name just below the lower border 

 of the thyroid cartilage. The little hyoid branch runs to the lower border of the 

 hyoid bone. The lingual artery arises from the j^arent trunk, opposite the tip of 

 the great cornu of the hyoid, and passes forwards just al)0ve the great cornu, and 

 thence to the side of the tongue. In the first part of its course, before it reaches 

 the hyo-glossus, it is curved, at first ascending, and then, having ascended slightly, 

 before it reaches the hyo-glossus, and wdiile it lies under it, its curve is gentle, with 

 the concavity upwards; beyond the hyo-glossus, as it lies on the muscles of the 

 tongue beneath the mucous membrane, it is tortuous. The lingual vein, it Avill be 

 remembered, does not run with its artery, but lies superficial to the hyo-glossus. It 

 receives the two small venae comites, which run with the lingual itself just before 

 it crosses the common carotid. The line of the facial artery (fig. 6b7), which 

 often arises with the lingual, has been given on page 1091. The occipital artery (fig. 

 667), starting on the same level as the facial (i.e. a point a little above and outside 

 the tip of the great cornu of the hyoid bone), follows a line drawn upwards and 

 outwards, first to the interval between the transverse process of the atlas and the 

 mastoid process, the former bone being felt just below and in front of the tip of the 

 latter; thence, lying in the occipital groove of the mastoid, the artery ascends 

 gradually, enters the scalp, together with tlie great occijiital nerve, at a point 

 about midway between the external occipital prominence and the mastoid process, 

 to follow, tortuously and superficial to the aponeurosis, the line of the lamlidoid 

 suture (p. 1088). 



The surface-marking of the digastric and omo-hyoid, which subdivide the 

 anterior triangle into the three smaller sul^triangks aliove descril^ed, should be 

 noted. The line of the posterior belly of the digastric corresponds to one 

 drawn from the apex of the mastoid |)rocess to a j^oint just above the junction of 

 the great cornu and body of the hyoid bone; and from this spot, Avhich gives the 

 point of meeting of the two tendons, one slightly curving upwards to a point just 

 behind the symphysis menti, would give that of the anterior belly. 



To trace the omo-hyoid, a line should be drawn from the lower margin of 

 the side of the hyoid bone ol)li(iuely downwards, so as to cross the common 

 carotid oi)posite the cricoid cartilage, and thence curving outwards under the 

 sterno-mastoid at the junction of its middle and lower thirds, and then on- 

 wards and still outwards, parallel with and a little above the clavicle, as far as 

 its centre. 



Posterior triangle. — This shows in its- lower part a wide depression, the supra- 

 clavicular fossa. Here the brachial plexus may be felt, and, by pressure down- 

 wards and backwards, just outside the outer margin of the sterno-mastoid, the 

 pulsation of the subclavian artery can be stopped against the first rib. This vessel 

 curves upwards and outwards from lieliind the sterno-clavicular joint to disapi)ear 

 behind the centre of the clavicle, the highest i)oint of the curve l)eing half an inch 

 to an inch above the bone. The artery on the left side lies more deeply than the 



