On account of their somewhat pungent taste, watercresses are used in many parts of the world as ingredients of salads, but they are, of all vegetables, the ones that are most liable to transmit disease to man, for in addition to the possibility of contracting in this way typhoid fever, dysentery, cholera, and the ordinary intestinal worms, the human being is apt to receive with them the eggs of the flukes, and the spores of the amoebæ that produce chronic tropical dysentery. As they are probably never grown under such conditions as to preclude the possibility of this danger, it would be the part of wisdom to absolutely refrain from their use.
_Onions, Leeks, Shallots, and Garlic._--Vegetables of this group are eaten either raw or cooked, and of all those consumed in the former state are least liable to transmit disease, owing to the fact that they are nearly always thoroughly peeled before being eaten. They have the advantage, furthermore, that they may be preserved for long periods of time in such a way as to be fit for food, and when properly cooked have a delicate flavor, and are quite wholesome although furnishing little food for the body. Garlic is never eaten as a vegetable, but serves as the basis for many of the delicate sauces for which the French cooks are so justly celebrated.
The tomato has been used as a food only within comparatively recent times, it having been formerly thought to be poisonous. Like the onion it may be eaten either raw or cooked, and if taken in moderation does not, as a rule, produce any serious harm. When eaten in greater quantities, both on account of the acid that it contains and its relatively small proportion of assimilable nutriment, the tomato is exceedingly prone to cause intestinal disturbances, and should rather be regarded as a fruit than a vegetable. Growing at some distance from the ground, it is rather less apt to convey diseases than the majority of vegetables eaten in a raw state.
While celery is generally eaten raw, it furnishes a palatable dish when cooked in milk. It should not be eaten by dyspeptics or children, particularly if raw. Similarly the cucumber has a well-merited reputation for producing dyspeptic disturbances. It is only eaten raw, is frequently served as a salad, and should be used only when very young and fresh, and eaten only by persons of sound digestion.