CHAPTER VII 
NUTRITION 
67. Organic and Inorganic. All substances belong to 
either one or the other of two classes of matter organic 
or inorganic. Organic substances are, for the most part, 
those which compose the bodies of animals or plants, past 
or present, or which have been, or may be, formed by the 
life-processes of living things. The possibility of synthe- 
sizing certain organic compounds (hydrocarbons) artifi- 
cially in the laboratory has broken down the hard and 
fast distinction, formerly recognized, between organic and 
inorganic substances. Bone, flesh, shells, bark, wood, 
leaves, gums and resins formed by plants, coal, sugar, 
flour, starch, cellulose, plant and animal juices, and all 
protoplasm represent organic substances. Inorganic sub- 
stances are those which have never been incorporated into 
the bodies of plants or animals, or if so, have since lost all 
evidence of that fact. Water, salt, iron, oxygen, carbon, 
glass, sulphur, air, represent inorganic substances. Some- 
times the line is hard to draw. Thus a piece of wood or 
of bone converted into charcoal may, if carefully handled, 
retain unmistakable traces of having formed a part of 
the body of an animal or a plant, but if the piece is ground 
in a mortar, a fine powder may result, that has lost all 
trace of its organic origin. Ordinarily, however, the 
two kinds of matter are easily distinguished, either by 
their structure or their known origin. So clearly distinct 
and unlike are they, that one entire branch of the science 
