122 THE HEAD AND NECK 



laryngeal nerve (p. 159) ; (2) the Crico-thyreoid Artery (p. 162) ; 

 and (3) a branch of supply to the sterno-mastoid (p. 115). 



The Lingual Artery (p. 145) arises from the external carotid 

 opposite the greater cornu of the hyoid bone. It makes an 

 upward loop, and then passes deep to the posterior border of 

 the hyo-glossus muscle, and gains the submaxillary region. 

 This loop permits the hyoid bone to be elevated without 

 putting an undue strain on the vessel. In ligature of the lingual 

 artery, preparatory to removal of the tongue, the first part of 

 the vessel is usually selected, as it is then secured before its 

 important branches to the tongue and the palatine tonsil are 

 given off. The incision is practically the same as for ligature 

 of the external carotid (p. 121). The greater cornu of the hyoid 

 bone is the superficial guide to the vessel, and the posterior 

 belly of the digastric is a convenient guide to the depth which 

 has been reached. Immediately below the muscle the hypo- 

 glossal nerve (p. 124) crosses the arterial loop, and tributaries of 

 the internal jugular vein often obscure both the nerve and the 

 artery. 



The External Maxillary (Facial) Artery arises from the 

 external carotid immediately above the lingual or occasionally 

 by a common trunk with it. Immediately after its origin it 

 passes upwards under cover of the stylo-hyoid and the posterior 

 belly of the digastric and enters the submaxillary region (p. 147). 

 The procedure already described for ligature of the lingual 

 artery may be followed in ligating this vessel. 



The Occipital Artery arises from the posterior aspect of the 

 external carotid artery at the same level as the external maxillary 

 (facial). It runs upwards and backwards along the lower border 

 of the posterior belly of the digastric, and disappears under 

 cover of the mastoid process and the muscles attached to it. 

 In the first part of its course it crosses superficial to the internal 

 jugular vein and the accessory nerve. As it crosses the latter 

 it gives off a branch of supply to the sterno-mastoid, and this, 

 when cut, may serve to indicate the proximity of the nerve. 

 Close to its origin the occipital artery is crossed by the hypo- 

 glossal nerve, which descends along the lateral side of the in- 

 ternal carotid and bends sharply forwards at this point (Fig. 39). 



The Accessory (Spinal Accessory) Nerve leaves the skull 

 through the middle compartment of the jugular foramen. At 

 first it lies between the internal carotid and the internal jugular 

 vein. Opposite the transverse process of the atlas the nerve, 



