1358 CLINICAL AND TOPOGRAPHICAL ANATOMY 



This space contains the submaxillary gland, and embedded in the gland is the external 

 maxillary artery, the facial vein lying superficial to the gland; deeper than the gland are the 

 submental vessels and the mylo-hyoid vessels and nerve. Posteriorly^, and separated from the 

 above structures by the stylo-mandibular ligament, which subdivides the triangle into a sub- 

 maxillary and parotid part, is the upper part of the external carotid artery running up into the 

 parotid gland, where it gives off its two terminal and the posterior auricular branches. More 

 deeply lie the internal jugular vein, internal carotid artery, and the vagus. The floor of the 

 triangle is formed by the m}'lo-hyoid, hyo-glossus, and superior constrictor. The lingual 

 artery maj^ be tied here, or, better, in order to get behind the dorsalis linguae, close to its origin, 

 by an incision similar to that for exposing the external carotid. 



The hypoglossal is a guide to the carotids and the occipital artery at the lower border of the 

 digastric, and farther forward, to the subjacent lingual, from which it is separated by the 

 hyo-glossus. 



The superior carotid triangle is bounded above by the digastric, below by 

 the omo-liyoid, and behind by the sterno-mastoid. It contains the upper part of 

 the common carotid and its branches, the external being at first 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 sympathetic nerves, and, for a short distance, the accessory, 

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



Ligature of the common carotid is usually performed at the 'seat of election,' where the 

 vessel is more superficial, above the omo-hyoid. An incision with its centre opposite the cricoid 

 is made 7.5 cm. (3 in.) long in the line of the carotid artery. The deep fascia along the an- 

 terior border of the sterno-mastoid having been divided, the cellular tissue beneath is opened up, 

 the omo-hyoid identified and drawn down or divided. The sterno-mastoid is next drawn well 

 laterally, and the artery felt for. At this stage, such veins as the communication between 

 the common facial and the anterior jugular and the superior and middle thyreoids may give 

 trouble. The sheath is next opened well to the medial side, opposite to the cricoid cartilage, 

 the ascending cervical, when seen, being avoided. If the internal jugular be distended, it may 

 be drawn aside with a blunt hook, or pressure made lightly in the upper angle of the wound. 

 The needle should be passed from the lateral side in verj^ close proximity to the lateral and back 

 part of the artery, so as to avoid the vein and vagus. Ligature below the omo-hyoid is rendered 

 more difficult by the presence of the anterior jugular, the pretracheal muscles, an overlapping 

 thyreoid gland, especially if enlarged, the greater depth of the artery, especially on the left side 

 and, here also, the closeness of the internal jugular. The collateral circtdaiion is given at p. 1360. 

 Ligature of the external carotid, otherwise difficult, is rendered very simple by first exposing the 

 bifurcation of the common carotid artery, the incision similar to the last being prolonged up- 

 ward. Here the facial and lingual veins and hypoglossal nerve cross the trunk, over which 

 also lie some of the deep cervical glands. The ligature is usually placed between the superior 

 thyreoid and lingual branches. 



Allusion must here be made to the chief structures liable to be met with in operations 

 on the neck. These are the internal jugular, the accessory, and phrenic nerves, the vagus 

 and hypoglossal, the thoracic duct, low down and deep on the left side, the oesophagus and 

 recurrent nerve in difficult operations on the thyreoid gland. Of these, the internal jugular is, 

 in some ways, the most important. _ Glands, tuberculous or epitheliomatous, are often adherent 

 to its sheath, especially those which drain the submaxillary group. When this condition is 

 present or suspected, it is always well to begin the dissection low down in the inferior carotid 

 triangle, where the structures are probablj' normal and the landmarks easy to identify. In 

 infective thrombosis of the transverse sinus the internal jugular is often tied opposite to the 

 cricoid cartilage, being either divided between two ligatures, or, if the thrombus has extended 

 downward, as much of the vein as is possible is removed. This vein contains only a single pair 

 of valves low down in the neck. In all operations here on it and the other two jugulars, the 

 risk of entry of air is to be remembered. The accessory and phrenic nerves are alluded 

 to on p. 1360. 



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

 behind by the sterno-mastoid, and in front by 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 thyreoid vessels, and to the medial side the 

 trachea, thyreoid gland, and a-sophagus. More deeply are the vertebral vessels; 

 on the left side is the thoracic duct. 



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

 The great cornu of the hyoid and the ala of the thyreoid are landmarks for the 

 origin of most of them. 



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

 pa.S8e.s dcjwiiward and forwiu'd to the back part of the thyreoid cartilage and upper part of the 

 thyreoid body. Many of its })ranclic.s are important in surgery. The superior laryngeal 

 j)erforateB the thyreo-liyoid meiribraiio. Tlie sterno-mastoid passes laterally into the middle 

 of the muscle, acro.s.s the carotid sheath. The crico-thyreoid crosses the space of the same name 

 just below the lower border of the thyreoid cartilage. The small hyoid branch runs to the lower 



