THE ART OF SCIENTIFIC INVESTIGATION 



janitor was on the job. Controlled experiments soon showed that 

 hypophysectomized chickens kept in darkness all died while 

 chickens lighted for 2 one-hour periods nightly lived indefinitely. 

 The explanation was that birds in the dark do not eat and develop 

 hypoglycaemia from which they cannot recover, while birds 

 which are lighted eat enough to prevent hypoglycaemia. Since 

 that time we no longer experience any trouble in maintaining 

 hypophysectomized birds for as long as we wish." 



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