320 THE ANIMALS AND MAN 



of the body below the heart) , and the coronary vein arising 

 in the walls of the heart. 



On the left side of the heart opening into the left auricle 

 there are four large veins, the pulmonary veins. Two of 

 these arise in the left lung and two in the right lung. Two 

 of these are shown at (i) in fig. 162. The large arteries 

 arise in the ventricles. The aorta (7) arises in the left 

 ventricle and carries the blood that is to be distributed to 



FIG. 163. Right cavities of the heart; auriculo-ventricular valves open, 

 arterial valves closed. (After Dalton.) 



the tissues of the body. Its branches go to the tissues 

 carrying blood laden with food and oxygen. 



The pulmonary artery (8) arises in the right ventricle and 

 carries the blood that is to be distributed to the air chambers 

 of the lungs. Its branches go to the walls of the lungs filled 

 with blood laden with carbon dioxide which is there ex- 

 changed for oxygen. The openings from the ventricles 

 into the arteries are guarded by semilunar valves shown 

 in fig. 162. Their position in action is shown in figs. 163 



