There is a famous study from the 1930s involving a group of orphanage babies who, at mealtimes, were presented with a smorgasbord of thirty-four whole, healthy foods. Nothing was processed or prepared beyond mincing or mashing. Among the more standard offerings--fresh fruits and vegetables, eggs, milk, chicken, beef--the researcher, Clara Davis, included liver, kidney, brains, sweetbreads, and bone marrow. The babies shunned liver and kidney (as well as all ten vegetables, haddock, and pineapple), but brains and sweetbreads did not turn up among the low-preference foods she listed. And the most popular item of all? Bone marrow.