THE VESSELS OPENING INTO THE HEART, l^l 



liquid, which makes the surfaces slippery, and allows 

 the heart to contract or expand with very little friction. 



16. The Vessels opening into the different Divisions of 

 the Heart (Fig.38). Veins bring back blood to the heart, 

 and open into the auricles. Arteries carry blood from 

 the heart, and start from the ventricles. 



The veins pouring blood into the right auricle are 

 named the upper (cs] and the lower (ci) hollow veins, or vena 

 cavce. They got this name because after death, when 

 most veins either collapse or are filled with blood, 

 these are often found distended and empty. 



One artery, P y springs from the right ventricle, and 

 carries to the lungs the blood brought to the right side 

 of the heart by the hollow veins. It is named the pul- 

 monary artery. 



The veins, pd,ps> which open into the left auricle are 

 named the pulmonary veins. They bring blood from the 

 lungs. 



One artery, A, arises from the left ventricle ; it is 

 named the aorta. As it proceeds from the heart it di- 

 vides, like the trunk of a tree, and at last its branches 

 reach every organ of the body except the lungs. 



17. The Beat of the Heart. The heart relaxes about 

 seventy times a minute, and takes blood from the veins; 

 it contracts after each relaxation and forces blood into 

 the arteries. This regularly alternating expansion and 

 contraction, is known as the beat of the heart. 



16. Function of veins? Place of opening into heart? Function 

 and place of opening of arteries ? What veins bring blood to right 

 auricle ? Why so named ? What is the pulmonary artery ? What 

 veins open into left auricle ? Whence do they bring blood ? What 

 is the aorta ? What becomes of its branches ? 



17. Describe the beat of the heart ? 



