Oyster Po'boys

1/2 cup milk

2 teaspoons salt

2 teaspoons black pepper

1 cup all-purpose flour

1 1/2 cups yellow cornmeal

2 teaspoons cayenne

3 dozen shucked small oyster s such as Kumamoto, drained

1 quart vegetable oil

1 (20-inch) loaf soft French or Italian bread (about 3 1/2 inches wide)

3/4 cup mayonnaise

2 cups thinly sliced iceberg lettuce

Special equipment: a deep-fat thermometer

Accompaniment: Tabasco