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 



69 



