If by chance you put by the remains of a dressed salad, it is good for nothing the next morning.
Finally, the oil must be pure olive oil of the best quality, and to ensure this it should bear the name of some well-known firm.

A good deal of the oil sold simply as salad oil, bearing no name, is adulterated, sometimes with cotton-seed oil.
SALAD, FRENCH LETTUCE, PLAIN .-- Clean one or more French lettuces (throw away all the leaves that are decayed or bruised), place these in a salad-bowl, and, supposing we have sufficient for two persons, dress the salad as follows:--Put a saltspoonful of salt and half a saltspoonful of pepper into a tablespoon.

Fill the tablespoon up with oil, stir the pepper and salt up with a fork, and pour it over the lettuce.

Now add another tablespoonful of oil, and then toss the lettuce leaves lightly together with a spoon and fork.

Allow one tablespoonful of oil to each person.
This salad would suffice for two.