4i6 BIOLOGY AND HUMAN LIFE 



We know, of course, that the farmer and the miller and the 

 baker do not exist primarily for the benefit of the beetle and her 

 family ; but we can understand why, from the narrow outlook 

 of the beetle, it looks for all the world as though the whole 

 universe were planned to revolve around her family and to 

 serve it. We must simply be on our guard against drawing 

 our own conclusions from the depths of our ignorance, as did 

 the beetle. 



Man is one of many thousands of species of animals living 

 upon the earth. Man and these other animals can live here 

 only because many species of plants are capable of p'oducing 

 food out of the inorganic materials in air, soil, and water. Some 

 of the animals and some of the plants are helpful or useful to 

 man in various ways. Some species are injurious to man, 

 directly (as certain parasites on his body) or indirectly (as 

 parasites upon organisms that he wishes to keep alive). As for 

 the rest, all we can say is that we have not yet found out how 

 we can use them or how they can affect our welfare ; but we 

 certainly cannot say that any of the numerous plants and ani- 

 mals exist because we need them or because there is some need 

 of our being injured by them, 



307. Utilities. The division of labor in carrying on the work 

 of the world has gone so far, and industry has developed so 

 much, that many kinds of materials are important for many 

 different uses that cannot be classified under food, clothing, and 

 shelter. Paper, for example, has come to be a necessity in every 

 branch of industry, business, government, or study. It is used 

 not only for books and magazines and newspapers but for cor- 

 respondence and records' and accounting; for papering our 

 rooms, waterproofing our roofs, and wrapping our groceries and 

 clothing; for making money and washtubs and car wheels. A 

 classification of the main directions in which materials are put 

 to use would make a very long and awkward catalogue, but the 

 main kinds of materials that are derived from plants and ani- 

 mals may be grouped somewhat according to the way in which 

 we make use of them. 



