By midsummer, cases number in the hundreds. Doctors fight about the cause. Air, water, Lake Michigan? The Trib is filled with photos: babies in iron lungs, Sister Kenny applying hot packs to paralyzed limbs, youngsters struggling on crutches. Mother scrubs apples, potatoes, peels the skin from peaches, grapes, insists on three baths a day, parsley juice at noon. Inside our stifling apartment, quarantined from playground or Plaza Theater germs, I watch friends hurry home in wet bathing suits. I live for Jack Armstrong: All-American Boy on WLS. One morning I wake with a rowboat stomach, fever. Fifty years, but I remember that plunge into the icy tub, hear her chair creak beside the bed as we wait for my legs to turn to wood.