The mystery of protoplasm is the mystery of life itself. We still do not know what makes protoplasm alive.

Protoplasm is the living part of all plants and animals. All organisms, plant or animal, are composed of cells. There may be many millions of cells, as in the human body, or there may be one as in the protozoa.

But the cell walls of all living things enclose the same life substance — protoplasm. In each cell, the protoplasm consists chiefly of two parts: the more solid central part called the nucleus, and the softer, more liquid part, the cytoplasm.

Each type of living thing has its own kind of protoplasm and the different types of cells within an organism have their own special forms of protoplasm. While protoplasm varies, 99 per cent of its bulk is made of carbon, hydrogen, oxygen, and nitrogen, with traces of many other elements.

When food is taken into a living body, it is first digested; that is, turned into liquid form. Then the digested food must be taken into and made a part of the protoplasm, a process known as assimilation. We still don’t know exactly what takes place during assimilation.

It is known that assimilation results in replacing worn-out protoplasm and making more protoplasm. In doing this, protoplasm builds up dead matter into living material and changes foreign material into substances like itself. Protoplasm also stores and releases all the energy that plants and animals have.

Protoplasm is sensitive to shocks from the outside. A strong light, or heat, will kill it. Chemicals attract or repel protoplasm; electric currents cause it to behave in various ways.

If science will someday solve the mystery of what makes protoplasm do what it does, we will understand more about the mystery of life itself.