188 GENERAL SCIENCE 



Nature has thus provided that plant life should help animal life, 

 and that animal life should help plant life. An atom of carbon 

 passes from a human being or animal to a plant, and from a plant 

 back to the human being or animal in the form of food. Thus the 

 cycle is complete. 



QUESTIONS 



1. What foods have you eaten to-day which contain (1) proteids, 

 (2) fats, (3) carbohydrates? 



2. Why should we chew our food well before swallowing? 



3. Why does alcohol produce a great deal of heat in the body? 



4. When could it be used as a medicine? 



5. Why do the Eskimos eat a great deal of fatty food? 



6. Why is it necessary to remove the carbon dioxide from the 

 body? 



7. Carbon monoxide unites with the hemoglobin of the blood. 

 Why is this dangerous to life? 



8. Why is the name " carbon cycle " applied to the process of 

 keeping the air pure? 



9. How many parts of oxygen does tne process 01 oreathing take 

 from the atmosphere? (Refer to formula.) 



10. How many parts of oxygen do plants return to the atmos- 

 phere? 



11. Where does all the carbon come from which makes up nearly 

 half the tree? 



12. Name the sources of the carbon which has made the redwood 

 trees of California. (About 4000 to 5000 years old.) 



13. Name the possible sources of carbon in the food you eat 

 to-day. 



14. How do the winds assist us in keeping the air pure in winter? 



15. Why is it objectionable to have plants in a sleeping room 

 during the night? 



