Applied Biology 111 



either plant or animal in 'origin. We eat plants and animals, the latter 

 depending on plants or other animals for their foods. The production, 

 transportation, proper preparation, and efficient use of foods have all 

 been materially affected by increased knowledge of biology. Through 

 animal experimentation, the vitamin content and chemical composition 

 of foods have been determined and their uses evaluated. More detailed 

 information in this connection will be found in the chapters on economic 

 importance of plants and animals. 



Many of our articles of clothing originate directly or indirectly from 

 plant or animal sources. The following typical examples will show the 

 validity of such a statement: (1) true silk from the silkworm, (2) cot- 

 ton from the cotton plant, (3) wool from the sheep and other animals, 

 (4) linen from flax plants, (5) furs from rabbits, skunks, opossums, foxes, 

 goats, muskrats, beavers, raccoons, (6) leather from prepared skins of 

 the cow, horse, pig, alligator, and other animals; (7) straw from the 

 stalks of wheat, rye, oats, and barley, (8) felt from the wool, fur, and 

 hair of animals, and (9) rubber from the juice of the rubber tree. 



Many of the materials for the construction of our furniture are of 

 plant or animal origin: (1) wood from plants, (2) willow furniture 

 from willow trees, (3) glue from the skins and hoofs of animals, (4) 

 leather from the prepared skins of various animals, (5) excelsior from 

 shredded wood, (6) paper from straw, bark, wood, and other fibers of 

 plants, (7) shellac from the resinous materials secreted by certain scale 

 insects, and (8) stains, varnish, and paint, at least in part, secured from 

 various plant materials. 



Unless we stop to reflect carefully and conscientiously, we do not 

 realize how many of our fuels are closely related to plants which were 

 formerly alive. The following brief suggestion in each instance will 

 suffice. Coal is really formed from plant materials for the most part. 

 Vegetation and stored solar energy, buried in the swamps of long ago, 

 have undergone many changes so that coal of one kind or another has 

 been formed. Wood is plant tissue which was once alive. It forms one 

 of our most valuable fuels. Natural gas is the product of biologic decom- 

 position of plant and animal remains of the past. This has probably 

 taken place under great pressures within the deeper strata of the earth. 

 Peat is one of the intermediate stages in the formation of coal and is 

 utilized in localities where coal is not readily available. Petroleum is 

 also formed by the decomposition of materials which to a great extent 

 were of animal and plant origin. Gasoline is secured by refining petro- 



