SITUS VISCERUM. 465 



1. Arteria pulmonalis, which lie the most anterior of all the 

 vascular trunks. Origin : ventriculus dexter, behind auric, sinis- 

 tra, covering the origin of the aorta. Divides on an elevation 

 with the third dorsal vertebra. The left trunk passes obliquely 

 backwards over vv. pulmonal. sinistr., before aorta descend, and 

 bronchus sinister with two branches to the left lung. The right 

 branch below arcus aorta, before bronchus dexter, behind aorta 

 ascendens with three branches to the right lung. From the angle 

 of division the lig. arteriosum (duct. art. Botalli] passes to the 

 concavity of arcus aortce, internal to nerv. vagus sinister. 



2. Aorta, arises from the left ventricle, ascends behind art. 

 pulmonalis as aorta ascendens from left to right, lying there be- 

 tween art. pulmon. (to the left) and v. cava sup. (to the right), 

 forms on an elevation with the second intercostal space the arcus 

 aortce, which passes from right to left and from before backwards 

 into the cav. mediast. post. ; and downwards as far as the fourth 

 dorsal vertebra. Here it descends as aorta descend, close to the 

 left side of the vertebral column, first close, then behind the (Eso- 

 phagus, and passes through hiat. aortic, in the region of the 

 twelfth dorsal vertebra into the abdomen. 



From its convexity arise 



a. Art. anonyma [art. brachio-cephalic.], lying the farthest 

 to the right and in front, behind manubrium sterni, before 

 trachea ; divides into carot. commun. and subclav. dextrce. 



b. Carotis comm. sinistra, at the commencement before, 

 then to the left of trachea and oesophagus, behind manubrium, 

 ven. brack, ceph. sinistra, and m. sterno-hyoideus. 



c. Subclavia sinistra, the farthest to the left and behind, 

 before the termination of m. longus colli. 



1 . Mammaria interna, arises from the ant. inf. surface 

 of subclavia, turns, at the commencement, forwards, then 

 downwards, passes inwards between two veins, before the 

 pleura on the inner surface of (one to seven) costal car- 

 tilages as far as proc. ensiform., where it bifurcates into 

 its two terminal branches, ram. musculo-phrenic. and epi- 

 gastricus. 



719. V. Vena azygos and hemiazygos (v. conjugate) pass 

 along on either side between crus extern, and med. diaphrag. into 

 the cavum mediast. post., passing close to the bodies of the dorsal 

 vertebrae as high as the eighth, where they unite in the ven. azy- 

 gos. This passes upwards to the right of the aorta and the ductus 



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