PROBLEM 235 263 



Sanitary Code of the city in which he lives and then by careful study to see which 

 sections are commonly broken and honored in the breach by the police or health 

 officials. Concerted action on the part of the younger members of a community 

 may bring about decided results for the betterment of a given neighborhood. Thus 

 our biology courses may become, in truth, courses in civic biology. 



Problem 234: How to ventilate my bedroom. (Home Problem.) 



NOTE. — This problem varies, depending on the number and position of the 

 windows in the room. Remember that air without direct draft is what is 

 desired. 



Method. — Recall the experiment of the candle and the box with 

 the holes in it. (See problem 214.) What happened when the 

 corks were removed from the two upper holes on one side only? 

 The two lower holes on one side only? The upper and lower 

 holes on one side only ? Now apply this principle to the room in 

 which you sleep. Make a diagram to show the air currents in 

 the room when you open the window for ventilation. Is this the 

 best way to have the air currents move? Why? 



Where should you place the bed and why? Should you use a 

 screen in your room ? If so, where should you place it ? 



Conclusion. — Make a diagram showing the best way to ventilate 

 your bedroom and give your reasons for thinking this is the best 

 way. 



Problem 235 : To compare the duster and the dry cloth with 

 the moist cloth in cleaning the schoolroom. 



Materials. — Sterile Petri dish with culture medium, broom, 

 oiled rags, oiled sawdust. 



Method. — Expose a sterile Petri dish culture in the schoolroom 

 for two minutes while members of the class dust with dry cloths 

 and broom. 



The same day have members of the class clean a neighboring 

 room, having the same conditions of dust and dirt, by means of 

 damp cloths and brooms with damp cloths tied or pinned over 

 the part that touches the surface of the floor. Use damp sawdust 

 on the floor. Expose Petri dish as in above test. 



Try the experiment in a third room, using oiled rags and oiled 

 sawdust. Expose Petri dish as in test number one. 



