Ergastic substances are non-protoplasm materials that one can find in cells. The living protoplasm of a cell is sometimes called the bioplasm and something else than the ergastic substances of the cell.
These are usually organic or inorganic substances that are products of metabolism, and include crystals, oil drops, gums, tannins, resins and other compounds that can help the organism in defense, maintenance of cellular structure, or just substance storage. During the lifetime of a cell, these can appear and disappear. They indicate some level of participation in life processes. Ergastic substances may appear in the protoplasm, in vacuoles, or in the cell wall.