HEART AND BLOOD VESSELS 



21 >3 



I I 





All to Back 



4^;;^ To stomach 



- 



— 



\ To Kid- 



' p^-^Jo Reproductive 

 organs 



To L.i 



■ 



The blood which is carried 

 into the lungs contains a large 

 amount of carbon dioxide 

 which gives it a dark color. 

 In the lungs the carbon dioxide 

 is given off and oxygen taken 

 up, so that when this blood is 

 returned to the left auricle, it 

 is of a bright red or " arterial " 

 color. 



Every time the heart beats 

 the blood is forced into the 

 arteries in waves which can be 

 felt in the wrist or neck by 

 placing the finger over an 

 artery. The wave is called 

 the pulse. By counting the 

 number of waves each minute, 

 the rate at which the heart beats 

 is determined. When a person 

 runs or takes violent exercise, 

 the pulse rate increases. It 

 is advisable to know what our usual pulse rate is, for 

 an increased pulse rate is sometimes an indication of 

 approaching illness. 



Lymph. — As the blood flows through the capillaries, 

 part of the plasma passes through the thin walls into the 

 spaces between the cells and bathes the cells. This fluid 

 which escapes from the capillaries is called lymph (llmf). 

 It is composed of digested food, water, and other sub- 

 stances. The cells take up the food which they nerd 

 and cast back into the lymph the wastes which they have 

 formed in the process of growth and repair. These spaces 

 between the cells are small and irregular in shape. The 



To Legs 



Figure 218. — Main Arteries 

 of Man. 



Compare with Figure 217. 



