PR()BLr:AI 2:35 2fi:i 



Sanitary Code of the city in which lie lives and then l)y careful study to hco which 

 sections are commonly broken and honored in the hrearh hy the \h>\\vv> or health 

 officials. Concerted action on the part of tlie younyer niend)or« of u conmiunity 

 may bring about decided results for the l)etternjent of a ^iven neinhlxirhood. Thu» 

 our biology courses may become, in truth, courses in rivir f>i»l»uy. 



Problem 234: How to ventilate nnj bedroom. (Ih.ine Prr»blein.) 



Note. — This problem varies, depending on llu- nuinl)tT and iM).sitir)n e)f the 

 windows in the room. Remember that air without direct draft i.s what im 

 desired. 



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

 the holes in it. (See prol)lem 214.) Wlial hapjx'ned when the 

 corks were removed from the two upper holes on one sid(» only? 

 The two lower holes on one side only? The uj)p(*r 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'.' ShouM yon uso 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 tliinking this is the best 

 way. 



Problem 2.3 r> : To C07nj)are the cJitster and the dry clotJi witJi 

 the moist cloth in cleaning the schoolroom . 



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

 oiled rags, oiled sawdust. 



Method. — Expose a sterile Petri dish cultinc in \\\v schoolroom 

 for two minutes while members of the class tlust with dry cU)tlis 

 and broom. 



The same day have members of the class clean a neighboring 

 room, having the same conditions of dust and dirt. l)y means of 

 damp cloths and brooms witli damp cloths tied or i)inned over 

 the part that touches the surface of the lloor. Ise 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 nunib(>r one. 



