246 



RESPIRATION AND EXCRETION 



In which dish has the greatest number of colonies developed? 

 Conclusion. — 1. In which room was the most dust (and 

 bacteria) stirred up? 



2. What do you consider the best method of cleaning a room? 



Froblem 217 : WTiat makes a crowded, closed room uncom- 

 foHoMe? 



Note. — it has recently been discovered that other factors besides the presence 

 of carbon dioxide in the air of a room make it uncomfortable. A little thoiight on 

 the following questions will convince you of this. 



Observations. — When a candle burns, what is given off be- 

 sides carbon dioxide? When a number of people are in a closed 

 room, what then would be given off from their 

 bodies ? 



Note. — The use of a wet and dry bulb thermometer 

 in a closed room containing people will show a decided in- 

 crease in the water content (humidity) of the air. 



Where does this water come from ? In 

 what condition does it get into the air ? 



What is your normal temperature ? Is that 

 the temperature of the air of the room? 

 What three substances are given off from 

 human bodies that might affect the air of 

 a closed room? Are you more comfortable 

 on a hot humid day or on a hot dry day? 

 What similar condition exists in a closed 

 room? 



NOTE. — The close odor noticeable in a closed room 

 containing people is due to certain organic wastes given 

 off from the body into the air. 



A Wet and Dry 

 Bulb Thermometer. 



Conclusion. — What factors cause discomfort in closed rooms 

 where there are many people? 



Problem 218 : To study the structure of the kidney. 

 Material. — A sheep kidney. 



Method and Observations. — An idea of the internal structure 

 of the kidney of man may be gained by examination of a sheep's 



