THE CIRCULATORY SYSTEM. 61 



Veins, blood-vessels leading to the heart. 

 Capillaries, uniting arteries and veins. 

 Three divisions of the circulation: 

 From heart to lungs and back to heart, for purifi- 

 WHAT? { cation pulmonary circulation. 



From heart to body and back to heart, for nutri- 



tion systemic circulation. 

 From veins of digestive organs through liver, for 



partial purification portal circulation. 



f Heart in chest, near middle. 



WHEBE? ^ Arteries, veins and capillaries distributed through- 

 ^ out the body. 



f To carry pure blood to all parts of the body. 

 J To gather up useless or waste material and carry 

 'I it to the organs which remove it from the 



(^ system. 



QUESTIONS. 



What can you say of the " wear and tear " of the body? 



What is the object of the circulatory system? 



What is the use of the blood? 



What are the organs and vessels of the circulation? 



Where is the heart situated? 



About how large is the human heart? 



Tell what you can about its purpose. 



How many chambers has the heart? 



Where is the right auricle? 



Where is the right ventricle? 



Where is the left auricle? 



Where is the left ventricle? 



What are the arteries? 



What kind of blood do the arteries usually carry? 



What are the veins? 



Do they usually carry pure or impure blood? 



Why do the veins have valves? 



What are the capillaries? 



