Experience in eating teaches much about differences in vegetables that is not so practically learned otherwise. But science alone can explain what is experienced and give information that living could not disclose without such study. Examination of the chemical composition of foods shows that some are much alike which may seem different, also the reverse.

Though refuse is purchased it is not usually in foods as eaten. The water in the edible portion of food is consumed. Though it does not nourish, it serves in body-regulation.

Which vegetables should be used together to supplement one another? Which should not be because they would duplicate one another? Which of those that have much starch seem more nearly like "green" vegetables? Are they in composition ? Parsnips and carrots are usually considered similar. See their composition. Note the similarity of the composition of pumpkins and cabbage.

For Complete Table of Food Composition, see Index.

Starchy, leguminous, and green vegetables have not only general differences but many specific variations within these groups. These alter the value of foods and their combination. Some foods nourish. Some make a diet palatable. Others by adding bulk promote peristalsis. Still others serve in regulation of body-fluids.

How foods are raised affects the dangers they may distribute. Celery, radishes, and such other ground-vegetables bring soil-dangers. All vegetables eaten raw, without skins to remove, as lettuce and salads, generally carry the dangers of soil fertilization, dust, and general handling. Their freshness need not be impaired to insure safety; if washed in boiling water and plunged into cold, crispness is revived and the food safer.