ALTERATIVE, an old term in the materia medica which comprised a group of substances which had, or were supposed to have, a specific influence on the nutritional processes of the body. They were mainly of the metal or metalloid class and included such things as iron, mercury, phosphorus, manganese and arsenic. Their mode of action was to "change" the metabolism of the organism as a whole or in any of its parts. Thus arsenic acts on the skin, causing changes in its rate of growth and nutrition. Iron exerts a profound influence on the blood. This rather vague group has fallen into disrepute and is not even mentioned in several of the more recent books on materia medica. The reason for this is that further research has brought to light the biochem ical reactions underlying the "alterations," and some of these excellent remedies have been removed to more scientific groups.