CIRCULATOEY SYSTEM 313 



right ventricle, and is produced in front into the 

 auricular appendix. 



2. The roots of the great vessels. 



a. Vessels opening into the right auricle. 



i. The right anterior vena cava returns blood from 

 the right side of the head, neck, and thorax, 

 and from the right fore-limb. It enters the 

 thorax at its anterior end, and runs back 

 along the inner side of the right lung, to open 

 into the right auricle by an aperture in its 

 dorsal wall. 



ii. The left anterior vena cava returns blood from 

 the left side of the head, neck, and thorax, 

 and from the left fore -limb. It runs back 

 along the inner side of the left lung, and 

 crosses between the heart and the root of the 

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

 auricle. 



iii. The posterior vena cava returns blood from all 

 parts of the body behind the diaphragm. It 

 enters the thorax through an aperture in the 

 diaphragm and runs- forwards, slightly to the 

 right of the median plane, to open into the 

 posterior end of the right auricle. 



b. Vessels arising from the right ventricle. 



i. The pulmonary artery conveys the venous blood 

 from the heart to the lungs. It arises from 

 the anterior border of the right ventricle in 

 the mid- ventral line, and arches over to the 

 dorsal surface of the left auricle, where it 

 divides into the right and left pulmonary 

 arteries, supplying the two lungs. 



c. Vessels opening into the left auricle. 



i. The pulmonary veins return the blood from the 

 lungs to the heart. There are two main 



