, ▁where ▁he ▁built ▁research ▁appar atus ▁for ▁profess ors ▁and ▁research ers ▁of ▁Boston - area ▁medical ▁schools , ▁and ▁produced ▁many ▁invent ions ▁over ▁the ▁following ▁years . ▁In ▁ 1 9 2 8 , ▁he ▁designed ▁a ▁Bar cro ft - W ar burg ▁appar atus ▁for ▁t issue ▁resp iration ▁studies . ▁In ▁ 1 9 3 0 , ▁he ▁designed ▁a ▁new ▁type ▁of ▁mic rom an ip ulator ▁which ▁was ▁valuable ▁in ▁early ▁phys i ology ▁studies ▁and ▁later ▁saw ▁use ▁in ▁assembly ▁of ▁electronic ▁components . ▁In ▁ 1 9 3 1 , ▁Em erson ▁developed ▁an ▁o xygen ▁tent ▁which ▁incorpor ated ▁an ▁improved ▁cool ing ▁system . ▁ ▁Work ▁on ▁the ▁iron ▁lung ▁Em erson ' s ▁father ▁encourag ed ▁him ▁to ▁work ▁on ▁an ▁artificial ▁resp ir ator ▁after ▁not icing ▁the ▁beginning ▁of ▁a ▁pol io ▁ep ide mic . ▁Em erson ▁thus ▁began ▁his ▁work ▁on ▁the ▁iron ▁lung ▁in ▁the ▁early ▁ 1 9 3 0 s , ▁impro ving ▁the ▁design ▁of ▁the ▁Dr ink er ▁lung . ▁Comple ted ▁in ▁July ▁ 1 9 3 1 , ▁Em erson ' s ▁lung ▁was ▁qui eter , ▁l ighter , ▁more ▁efficient , ▁and ▁che aper . ▁With ▁a ▁$ 1 0 0 0 ▁price ▁tag , ▁it ▁sold ▁for ▁less ▁than ▁half ▁the ▁price ▁of ▁Dr ink er ' s ▁make . ▁Dr ink er ▁threatened ▁legal ▁action ▁against ▁Em erson , ▁and ▁later ▁file d ▁a ▁law