A word must be said of this group of adjuvants to food. They possess no nutritive value, but often aid digestion by stimulating the organs to secrete digestive juices in larger amounts and they make food more palatable. The most important of them are mustard and pepper. Various spices and condiments are employed, chiefly for their flavor or for certain oils, such as vanilla and lemon. Sugar is of great value both as a food and as a condiment for it makes food more palatable. Saccharin and dulcin must be substituted for sugar when the latter is not well digested or assimilated. They are, however, condiments, and not foods. Vinegar is useful both as a flavoring agent and because it helps to soften hard muscle-fibers and cellulose. For the latter purpose it is frequently added to preparations of lobster and to raw green vegetables, such as lettuce, celery, sorrel, cucumbers, and tomatoes, when used as salads.