20 FEEDING FARM ANIMALS 



Respiration. When the impure blood passes 

 through the lungs, carbonic acid gas and other 

 impurities are held back and in breathing are ex- 

 haled and thrown out of the system. At the same 

 time oxygen is taken in with' great greediness by 

 the cells of the blood, which distribute it where 

 needed in all parts of the body. When plants are 

 growing, oxygen is released and thrown into the 



DISTRIBUTION or CAPILLARIES 



JN POSTERIOR EXTREMITIES, 



RIGHT 

 VENTRICL" 



How THE BLOOD CIRCULATES THROUGH THE BODY 



The blood is collected from the body and delivered into the right auricle, 

 which on contracting, forces the blood into the right ventricle; this in turn 

 contracts and forces the blood into the lungs, where oxygen is taken on and 

 carbonic acid gas and other impurities are thrown off. From the lungs the 

 blood is returned to the left side of the heart and distributed through arteries 

 and capillaries to all parts of the body. 



air. At the same time, by means of leaves, the car- 

 bonic acid gas is drawn in and used in the construc- 

 tion of the plant compounds. This was got from 

 the air. The animal, in performing its functions 

 and in building its tissue, inhales oxygen from, and 

 exhales carbon dioxide into, the air. Thus it is that 

 animals use what is waste to the plant and the 

 plants use what is poison to the animal. 



