Cut off the stalks from 3 or 4 heads of lettuce, pick off all the decayed and withered leaves, break the tender green leaves apart one by one and remove the thick veins; put the lettuce into cold water, rinse well and let it lay in ice water for 1/2 hour or longer; shortly before serving drain the lettuce in a colander; then put it in a napkin, shake out well and use as directed.