32 APPLIED PHYSIOLOGY 



stances dissolved in it make it good or bad for use. Really 

 pure water has a flat taste, and is unfit for drinking. Air 

 in the water gives it a pleasant taste. Water often dis- 

 solves lime from the soil so that it does not easily form a 

 lather with soap. We call such water hard. Rain water 

 is soft y for it has no lime. 







How impurities may get into a well. 



58. Impure water. Water dissolves many substances 

 over which it runs, but only a few of these are harmful. 

 When it stands in lead pipes for some hours, it dissolves a 

 little poisonous lead. If the water that has stood in the 

 pipes is thrown away, the running water will be safe for use. 



Almost the only other dangerous substance found in 



