The morning began with a first gamy whiff of what lay in store. Shortly after 9 a.m., Bradley Martin, his assistant Jin-Quang Kuang and a researcher named Ellen Flynn marched along a dimly lit, institutional-tiled corridor at the Johns Hopkins Hospital in Baltimore. After pausing to take a deep breath, they pushed through a green door and entered a small room where several robust Yorkshire pigs greeted them with braying squeals and frothing curiosity. Flynn wheeled a heart-imaging echocardiogram machine into the narrow aisle between the cages, and then Martin, a flimsy yellow surgical gown covering his blue jeans and sports shirt, stepped gingerly into one of the cages and gently wrapped an arm around the huge porker, a gesture that wavered between a hug and a headlock. "All those years of graduate school," Martin grunted over his shoulder, "are finally paying off."

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