HOUSING AND HYGIENE 



25 



and ranging in position from the neck to the abdomen, with a 

 single median sac located in the cavity of the thorax. 

 Besides opening into the lungs, these sacs communicate 

 directly with the cavities of most of the bones of the body, 

 with the exception of those of the forearm and hand of the 

 wing and those below the hock-joint of the leg. 



Fig. 132 



A farm poultry-house: no light, no ventilation. (Courtesy of Purdue 

 Agricultural Experiment Station.) 



This elaborate system for gathering moisture from every 

 part of the body trunk is working at a distinct disadvantage 

 when the air which must be depended upon to take up the 

 moisture vapor is already laden with it. 



Such a condition is debilitating to the system as well as 

 fatal to production. It is a law of universal application that 

 a debilitated condition always means weakened defensive 

 powers and a greater susceptibility to disease. 



Moisture is one of the essentials of the development of 

 disease germs in common with all other bacteria. The 

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