Venetian Soup

From 1922:

An Italian recipe.
Take 6 eggs, half a lemon, 1 French roll, pepper and salt, 2 quarts medium stock. Beat up the yolks of the eggs in a saucepan with a little lemon juice and a seasoning of salt and pepper. Stir in the cold stock slowly, then place over a slow fire and continue stirring till thick without letting the soup boil. Slice the roll in a tureen and pour over it the soup. Time, 20 minutes. Seasonable at any time.