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 ventilat- 

 ing a room ? 



Demonstration. — Best methods of dusting and cleaning. 



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



To the Teacher. — Respiration, especially, gives ample opportunity for simple 

 experiments which can be performed by the pupil. The changes of blood within 

 the lungs are easily demonstrated by any pupil. The mechanical factors in respi- 

 ration are easily shown. 



The subjects of ventilation and proper care of the home give innumerable 

 opportunities for practical experiments by the pupils. Care must be taken, how- 

 ever, that the pupils do not gain wrong impressions from experiments on the burn- 

 ing of the candles within a box. Recent investigations make it seem certain 

 that carbon dioxide as a factor in ventilation is less to be reckoned with than the 

 humidity and heat factors. Experiments with wet and dry bulb thermometers 

 should be tried in closed rooms to show the increase in the water content of air and 

 its effect upon the human organism. Other experiments will doubtless commend 

 themselves. 



Experiments to show proper methods of dusting and cleaning should be tried 

 at home and reported upon by groups of pupils. In this way more ground may be 

 covered in a given time and more individuals interested in the work. 



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