THE ANTERIOR PART OF THE NECK 231 



secure the hypoglossal nerve and the lingual vein, the vein lying below 

 the nerve. Displace the lingual vein and the hypoglossal nerve upwards ; 

 cut through the fibres of the hyoglossus, immediately above and parallel 

 with the great cornu, and display the lingual artery, which in this position 

 lies immediately above the great cornu, parallel with the lingual vein but 

 separated froni it by the hyoglossus muscle. 



All the structures which have been mentioned above will be met with 

 in the dissection of other regions, when a full account of them will be given. 



Turn next to the carotid triangle, so called because it 

 contains parts of the common, internal, and external carotid 

 arteries. It is bounded posteriorly by the anterior border of 

 the sterno-mastoid ; above and anteriorly by the posterior 

 belly of the digastric ; and below and anteriorly by the anterior 

 belly of the omo-hyoid. 



Dissection. Trace the anterior facial vein from the digastric triangle 

 across the superficial surface of the posterior belly of the digastric to its 

 posterior border, where it unites with the posterior facial vein, which is 

 descending from under cover of the lower end of the parotid gland. The 

 trunk formed by the union of the anterior and posterior facial veins is the 

 common facial vein. Trace the common facial vein downwards and 

 posteriorly to its union with the internal jugular vein, at or under cover 

 of the anterior border of the sterno-mastoid. Remove the deep fascia 

 and the areolar tissue, and the lymph glands which lie in the angle between 

 the posterior belly of the digastric and the anterior border of the sterno- 

 mastoid, below the lower end of the parotid gland ; secure the lingual 

 vein, which passes backwards from the tip of the great cornu of the hyoid 

 bone to join the internal jugular vein ; and the hypoglossal nerve as it 

 crosses anteriorly at a higher level, superficial to the internal and external 

 carotid arteries. As the nerve turns anteriorly across the large arteries it 

 is itself crossed, superficially, by the sterno-mastoid branch of the occipital 

 artery, and it gives off its descending branch. Trace the descending 

 branch downwards, in the fascia which lies superficial to the lower part 

 of the internal and the upper part of the common carotid arteries, to 

 the point where it disappears under cover of the anterior belly of the 

 omo-hyoid, avoiding injury to the lingual, common facial, and superior 

 thyreoid veins ; l and secure the communicating branch, from the second 

 and third cervical nerves, which joins its posterior aspect. The latter 

 nerve may cross either superficial or deep to the internal jugular vein. 

 Return to the hypoglossal nerve at the point where it gives off its descending 

 branch, and trace it anteriorly to the upper aspect of the posterior end 

 of the great cornu of the hyoid bone, where it gives off the branch of 

 supply to the thyreo-hyoid muscle. Trace the branch into that muscle 

 below the level of the great cornu, then follow the trunk of the hypoglossal 

 anteriorly to the digastric triangle. Note that as it runs anteriorly it 

 passes deep to the posterior belly of the digastric and the stylo-hyoid 

 muscle, and superficial to the hyoglossus, which ascends to the tongue from 



1 The lingual vein may join the common facial vein, in which case the 

 latter usually enters the internal jugular opposite the interval between the 

 hyoid bone and the thyreoid cartilage, as in the specimen depicted in Fig. 93. 

 The superior thyreoid vein joins the internal jugular or the common facial 

 vein opposite the thyreo-hyoid interval. 

 II 15 c 



