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 Inorganic and Organic Matter.—Test for Minerals.—The earth was once in a molten condition, which would have destroyed any combustible material if any had then existed. Before plants and animals existed, the earth consisted mostly of incombustible minerals, known as inorganic matter. Substances formed by animals and plants are organic matter, so called because built up by organized or organ-bearing or living things; starch is an example, being formed in plants. Organic substances are composed chiefly of carbon, oxygen, hydrogen, and nitrogen. (See page 1 of "Animal Biology.") Coal-oil, and all combustible materials have their origin in life. Hence, burning to find whether there is an incombustible residue is also a test for minerals. Meat, bread, oatmeal, bone, wood, may be tested for mineral matter by burning in a spoon held over a hot fire, or flame of gas or lamp. The substance being tested should be burned until all black material (which is organic carbon and not a mineral) has disappeared. Any residue will be mineral matter.

Protoplasm.—Inside the cells of plants and animals is the living substance, known as protoplasm. It is a structureless, nearly or quite colorless, transparent jelly-like substance of very complex and unstable composition. Eighty per cent or more is water; the remainder is proteid, fats, oils, sugars, and salts. Protoplasm has the power of growth and reproduction; it can make living substance from dead or lifeless substances. It has the power of movement within the cell, and it is influenced (or is irritable) by heat, light, touch, and other stimuli. When protoplasm dies the organism dies.

Physics is the science that treats of the properties and phenomena (or behavior) of matter or of objects; as of such properties or phenomena or agencies as heat, light,