xviil GENERAL INTRODUCTION 



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 con- 

 sisted mostly of incombustible minerals, known as inorganic 

 matter. Substances formed by animals and plants are 

 organic tnattcr, 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 I 

 of "Animal Biology.") Coal-oil, and all combustible ma- 

 terials 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 struc- 

 tureless, nearly or quite colorless, transparent jelly-like 

 substance of very complex and unstable composition. 

 Eighty per cent or more is water ; the remainder is pro- 

 teid, fats, oils, sugars, and salts. Protoplasm has the 

 power of growth and reproduction ; it can make living sub- 

 stance from dead or lifeless substances. It has the power 

 of movement within the cell, and it is influenced (or is irrita- 

 ble) by heat, light, touch, and other stimuli. When proto- 

 plasm 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, 



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