Protoplasm << PROH tuh `plaz` uhm >> is a term that means the living matter of cells. The term is little used by modern biologists because it is not specific. Johannes Purkinje, a Czech physiologist, first used it in 1839. At that time, scientists knew that all living things are made up of cells that seemed to contain a jellylike material. Purkinje named this material protoplasm—from Greek words meaning first formed or pronounced molded—to indicate it was the most basic substance of life.
Since that time, more powerful microscopes and advanced biochemical techniques have revealed more about the structure of the cell. Scientists have discovered that the jellylike material of cells is actually a complex mixture of proteins and other substances. The composition of this mixture varies among different types of cells and even from one part of a cell to another. Thus, biologists today use the terms cytoplasm, nucleoplasm, and plasma membrane to describe specific parts of the living cell matter (see Cell (Inside a living cell)). But the word protoplasm is sometimes used to describe the substance of a type of slime mold lacking cell boundaries at one stage of its life cycle.
