298 SPECIAL ANATOMY. 



left and behind the anonyma, is longer than the Carotis communis dextra, and 

 passes obliquely before the trachea and to the left of it and the thyroid gland. 

 3. Subdavia sinistra, arises the farthest backwards and to the left, from the 

 arcus aortce, is longer, rather thicker, and ascends in a rather straighter direc- 

 tion than the subdavia dextra, to the left and externally. 



541. A. Carotis communis, the common carotid artery. 



Origin : the right arises from the A. anonyma, the left close to 

 A. subclav. dextra / on the right close to the trachea. The left 

 from the centre of arcus aortce itself. -Course : both carotids as- 

 cend obliquely upwards and outwards, from the chest into the 

 neck, and terminate at the superior border of the larynx with 

 an enlargement, so that they diverge from below (where trachea 

 and oesophagus) upwards (where larynx and pharynx lie between 

 them). 



Situation : 1. In the chest. 



a. The right Carotis commences only very shortly before the 

 superior border of the Manubrium sterni, from which it is se- 

 parated by ven. jugular, comm. sinistra. 



b. The left, about one inch before its exit, lies behind V. sub- 

 clavia sinistr., mm. sterno-hyoidei and thyreo'idei and sternum; 

 before trachea and oesophagus, Artt. subclavia and vertebr. sinist. 



2. In the neck : in a sheath offasc. cervicalis ; the inferior half 

 of the anterior surface covered by mm. sterno-thyreoideus, sterno- 

 mastoideus ; the centre by the tendons and the superior belly of 

 m. omo-hyoideus ; the superior half in the trigonum cervicale su- 

 perius only by platysma-myoides. The posterior surface is sepa- 

 rated from the vertebral column by mm. rectus capitis and long, 

 colli, and (below) Ven. thyreoidea inferior. Internally are situated : 

 trachea, (Esophagus, larynx, and thyroid gland. Externally : V. 

 jugularis interna. Between these and the Carotis: ram. descend. 

 N. hypoglossi (the farthest forwards), N. vagus (inwards), N. 

 Sympathicus (externally and behind). The first passes down- 

 wards only to the centre, the two last vertically along the entire 

 cervical portion of the carotis. 



Branches pass off from the Carotis communis as exceptions 

 only, as : Art. thyreoid inf. (and media) ; but it divides into two 

 terminal branches, into Carotis externa and interna. 



542. I. Carotis externa s.facialis. 



Origin : on an elevation with the superior border of the larynx, 

 internal to and before Carotis interna. Termination : at the neck 

 of Condylus mandibulce. Course: in adult slightly undulating ; 



