XXII. RESPIRATION AND EXCRETION 



Problems, — A study of respiration to find out: — 

 {a) What changes in blood and air take place within the 

 lungs. 

 (b) The mechanics of respiration. 

 A study of ventilation to discover : — 

 {a) The reason for ventilation, 

 (b) The best method of ventilation. 

 A study of the organs of excretion. 



Laboratory Suggestions 



Demonstration. — Comparison of lungs of frog with those of bird or 

 mammal. 



Experiment. — The changes of blood within the lungS. 



Experiment. — Changes taking place in air in the lungs. 



Experiment. — The use of the ribs in respiration. 



Demonstration experiment. — What causes the filling of air sacs of the 

 lungs ? 



Demonstration experiment. — What are the best methods of ventilating 

 a room ? 



Demonstration. — Best methods of dusting and cleaning. 



Demonstration. — Beef or sheep's kidney to show areas. 



Necessity for Respiration. — We have seen that plants and 

 animals need oxygen in order that the life processes may go on. 

 Food is oxidized to release energy, just as coal is burned to give 

 heat to run an engine. As a draft of air is required to make fire 

 under the boiler, so, in the human body, oxygen must be given so 

 that food in tissues may be oxidized to release energy used in 

 work. This oxidation takes place in the cells of the body, be they 

 part of a muscle, a gland, or the brain. Blood, in its circulation 

 to all parts of the body, is the medium ivhich conveys the oxygen to 

 that place in the body where it will be used. 



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