10 



(c) The right auricle, dorsal in, position to the base of the right 



ventricle with an auricular appendix. 



(d) The left auricle, anterior to the left ventricle, with an auricular 



appendix. 

 2. The great vessels. 



(a) Vessels opening into the right auricle. 



(1) The right superior vena cava, running along the inner side 



of the right lung, to open on the dorsal wall of the right 

 auricle. 



(2) The left superior vena cava, running along the inner side 



of the left lung, to open into the left side of the right 



auricle. 

 (S) The inferior vena cava, piercing the diaphragm and running 



forwards, a little to the right of the middle line of the body, 



to open into the posterior end of the right auricle. 

 (6) Vessels arising from the right ventricle. 



( 1 ) The pulmonary artery, arising from the anterior border of the 



right ventricle and arching over to the dorsal surface of the 



left auricle, where it divides into right and left pulmonary 



arteries. 



(c) Vessels opening into the left auricle. 



(1) The pulmonary veins, opening on the dorsal surface of the 

 left ventricle. 



(d) Vessels arising from the left ventricle. 



(1) The aorta, arising from the middle of the base of the heart 

 behind the root of the pulmonary artery, running forwards, 

 then arching over to the left side, and descending at the left 

 side of the vertebral column. The ductus arteriosus, an 

 obliterated vessel connecting the aorta with the pulmonary 

 artery. 

 The veins. 



1. The system of the vense cavae. 



(a) The right superior vena cava formed by — 



(1) The right subclavian vein, from the fore-limb and shoulder. 



(2) The right external jugular vein, from the side of the neck, 



formed by the union of the anterior and posterior facial veins. 



(3) The right internal jugular vein, close to the trachea, 



joining the external jugular vein at its point of union with 

 the subclavian. 



(4) The vena azygos, lying close to the vertebral column on the right 



side of the aorta, and passing round the right side of the 

 oesophagus and trachea to join the vena cava close to the 

 auricle. It receives seven or eight pairs of intercostal veins. 



(5) The anterior phrenic vein, passing forwards from the diaphragm 



along the inferior vena cava. 



