CHAPTER LXXIX 



THE NATURAL LIGHTING OF FARM BUILDINGS 



Development. If a comparison be made between the 

 farm buildings of twenty-five years ago and those which are 

 entitled to be called modern, it would be found that one of the 

 principal differences lies in the natural lighting, or the amount 

 of window surface provided. This change is due largely to a 

 more general recognition of the value of light as a sanitary 

 agent. 



Purpose of Natural Lighting. The natural lighting of 

 farm buildings has a three-fold purpose: (1) The principal 

 purpose, to make the buildings more sanitary by destroying 

 disease germs; (2) to provide a more convenient and pleasant 

 place for the attendants to care for the animals; and (3) to 

 provide more pleasant and comfortable quarters for the 

 animals to feed and live in. As stated, the principal reason 

 for providing adequate natural light for farm buildings is to 

 secure sanitary quarters for the animals. Direct sunlight is 

 far more powerful and destructive to disease germs than 

 diffused or reflected light, and for this reason as much direct 

 sunlight as possible should be provided. Usually but a short 

 time, a few hours, is required to kill germs by direct sunlight. 



In regard to the value of diffuse light for destroying 

 germs, Dr. Weinzirl, an eminent bacteriologist, is quoted in 

 King's book on Ventilation as follows: "The shortest time 

 in which diffuse light in a room killed the bacillus of tuber- 

 culosis was less than a day, and the longest time was less than 

 a week; generally, three or four days of exposure killed the or- 

 ganisms. Some pus-producing bacteria required a week's 



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