CHAPTER XXVI 

 HEATING AND VENTILATION 



We have been considering the relations between atmos- 

 phere and man out-of-doors. But since most of us spend 

 much of our lives indoors, it is important also to consider 

 the atmosphere in its relation to our indoor life. 



Houses. Houses are an excellent invention. They 

 and our clothing are the principal means whereby we satisfy 

 the shelter need. It is difficult to tell which of these 

 shelter providers was invented first. Primitive man prob- 

 ably began constructing or rinding shelter among the rocks, 

 or among the trees of the forest, just as soon as he began 

 to clothe himself with the skins of wild animals or with 

 rude garments made from the fibrous parts of plants. 



Houses undoubtedly provide excellent protection from 

 rain and wind and, usually, from cold. The only objec- 

 tion to them is that they may interfere (especially when 

 artificially heated) with the supply of fresh air that we 

 need. So we often hear it said that people stay indoors 

 too much. We hear a good deal about the benefits of 

 outdoor life, which means, besides exercise, plenty of fresh 

 air and sunshine. These blessings indoor life cannot pro- 

 vide. Since man developed as an outdoor rather than as 

 an indoor creature, his body is fashioned for outdoor rather 

 than for indoor life; it pales and sickens if denied its 

 heritage of fresh air, exercise, and sunshine. So there is 

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