Medicine: In Mothers' Milk

Because polio is usually a warm-weather disease of temperate zones, doctors jumped at the chance to study a polio outbreak two winters ago among Eskimos at deep-frozen Chesterfield Inlet, in Canada's Northwest Territories just below the Arctic Circle. One striking fact was soon evident: though infants under three got polio just as older children and adults did, none of the infants suffered the devastating paralytic stage of the disease. And the infants up to three years old, following local Eskimo custom, were still being nursed at their mothers' breasts.*

The coincidence was so...