Fig. 6i. Anterior Aspect of the Neck, Deep Layer. Adult. 



Position of the head as in last figure. T/ie Superficial Veins are left as stumps., 

 both Sterno-Cleido- Mastoid Muscles are cut off near their attachments ; on the 

 left side, Stemo-Hyoid, Sterno-Thyreoid and tipper belly of Omo-Hyoid Muscles 

 have been removed. Both Submaxillaj-y Glands have been taken aivay : removal 

 of the right Digastric Stylo-Hyoid and Mylo-Hyoid Muscles has given a good 

 exposure of the fioor of the month from below. 



The Common Carotid Artery enters the neck behind the Sterno-clavicular 

 articulation, externally to Trachea and Oesophagus. Slightl}' inclined outwards at 

 first, it soon runs vertically upwards, without giving off an}' branches. At the 

 level of the upper border of the Thyreoid Cartilage, it divides into External and 

 Internal Carotid (just below the bifurcation, is the most suitable spot for liga- 

 turing the Common Carotid, because it lies superficially here being covered onty 

 by skin, Plat3'sma and Superficial Cervical Fascia). When the fascia is incised, 

 the Sterno-Cleido-Mastoid Muscle drops backwards. External to the Artery lies 

 the Internal Jugular Vein, which, when filled, covers the outer aspect of the Artery. 

 It receives the Superior Thyreoid Vein and, above the bifurcation of the Carotid, 

 the Facial Vein ; the Carotid Artery and Jugular Vein are enclosed in a common 

 fascial sheath (Carotid sheath); they are crossed by the Omo-Hj'oid which runs 

 downwards and outwards. In front of them lies the Descendens Hypoglossi. 

 Between the Artery and ^^ein, somewhat posteriorly above, but more anteriorly 

 below runs the Vagus Nerve. External to the Jugular Vein, the Phrenic Nerve 

 descends on the Scalenus Anticus Muscle. 



The size of the Thyreoid Gland varies considerabl}' according to the 

 frequency of Goitre in certain districts. The isthmus connecting the 2 lobes lies 

 on the trachea, covering the 2ncl, 3rd and 4th rings. It may, however, extend 

 higher up or lower down (cf. Fig. 62). It often gives off a process upwards, the 

 Pyramidal Lobe (Pyramid of Lalouette) ; this lobe, as shewn in our figure, may 

 also arise from one of the lateral lobes ; it often runs to the Hj'oid bone. The 

 isthmus, being fixed to the trachea by connective tissue, follows the movements 

 of that organ. This is of importance in the diagnosis of tumours of the Neck. 

 The lateral lobes are covered by the Sterno-Hyoid, Sterno-Th3'^reoid and Omo- 

 Hyoid Muscles. Their size varies markedly. They receive blood from the Superior 

 Thyreoid Artery a branch of the External Carotid and from the Inferior Thyreoid 

 Artery, which arises from the Subclavian and runs upwards behind the Common 

 Carotid. 



The Larynx is subcutaneous, the Trachea lies under the skin at its com- 

 mencement but runs to a deeper level the nearer it approaches the Thorax. In 

 front of its upper portion is the Thyreoid Gland; lower down, fatty tissue; at 

 this point the Thymus is just visible above the sternum in children. 



