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APPLIED PHYSIOLOGY 



House fly, greatly magnified. 

 Showing its hairy body and legs, to which filth and bacteria may adhere. 



hard-shelled pupas, from which full-grown flies emerge in about another 

 week. There could be no house flies if there were no manure piles, 

 garbage heaps, or other collections of decaying substances in which the 

 young flies could grow. Stables and barnyards should be kept dry and 

 clean, and no collections of decaying substances of any kind should be 

 allowed to exist. Then we should be free from flies in summer as well 

 as in winter. 



