ell . ▁ ▁From ▁ 1 9 4 7 ▁to ▁ 1 9 4 9 , ▁Ca ud ill ▁conducted ▁research ▁on ▁Japanese ▁Americans ▁in ▁Chicago , ▁who ▁had ▁recently ▁been ▁released ▁from ▁intern ment ▁during ▁World ▁War ▁II . ▁ ▁Ca ud ill , ▁and ▁the ▁team ▁he ▁worked ▁with , ▁were ▁interested ▁in ▁the ▁social ▁and ▁psych ological ▁adjust ment ▁process ▁that ▁these ▁Japanese ▁Americans ▁under w ent ▁after ▁release ▁from ▁intern ment ▁cam ps . ▁ ▁Cont ribution s ▁to ▁Medical ▁Anth rop ology ▁After ▁receiving ▁his ▁Ph D ▁from ▁Chicago , ▁Ca ud ill ' s ▁interests ▁turned ▁from ▁psych ological ▁anth rop ology ▁to ▁medical ▁anth rop ology . ▁ ▁Ca ud ill ▁was ▁able ▁to ▁conduct ▁his ▁first ▁major ▁field work ▁in ▁medical ▁anth rop ology ▁after ▁he ▁was ▁invited ▁by ▁Y ale ▁Medical ▁School ▁to ▁study ▁the ▁social ▁hier arch ies ▁within ▁the ▁Y ale ▁Psych iat ric ▁Institute . ▁ ▁As ▁a ▁condition ▁of ▁the ▁field work , ▁Ca ud ill ▁under to ok ▁particip ant ▁observation ▁by ▁living ▁as ▁a ▁" pat ient " ▁in ▁the ▁Psych iat ric ▁Ward ▁for ▁two ▁months , ▁with ▁his ▁identity ▁as ▁a ▁research er ▁known ▁only ▁to ▁the ▁super int endent ▁of ▁the ▁hospital . ▁Ca ud ill ▁reported ▁his ▁conclus ions ▁from ▁this ▁field work ▁in ▁" So cial ▁Str ucture ▁and ▁Inter action ▁Process es ▁on ▁a ▁Psych iat ric ▁Ward ," ▁published ▁in ▁the ▁American ▁Journal ▁of ▁Orth ops ych iat ry ▁in ▁