'4 l i : *-" Li t /A .ELEMENTARY BIOLOGY 



found out also that there is an added danger in the greater 

 amount of handling that all food materials receive in passing 

 from the places where they originate to the places where they 

 are finally used up. Again, every time a person suffering 

 from any one of certain diseases comes in contact with another 

 person, there is danger of passing the sickness on. Many of 

 these things were not known fifty years ago, and very many 

 of the regulations which have been adopted depend upon 

 principles derived from a study of living things. 



3. Biology related to wealth. In the second place, it has 

 been found that many of the natural possessions or resources 

 of the country have been so wastefully handled in the past 

 that our, growing population is likely to run out of things that 

 are absolutely necessary for comfortable living, unless we 

 find some better ways of using our forests, our streams, 

 our soil, and so on. And we must be guided in our use 

 of these resources by an understanding of the principles that 

 can be learned only from a study of living things. The same 

 is true with regard to the protection of various wild animals 

 and plants against extermination, where these happen to be 

 of value to mankind directly or indirectly. And, on the other 

 hand, it is an understanding of biology that makes possible 

 the most effective fight against those plants and animals which 

 happen to be injurious to the living things that are useful 

 to us. In this connection, too, we have learned that it is 

 possible to get a much larger return for our labor, in the way 

 of raising plants and animals for human use, by applying the 

 principles of biology to agriculture, horticulture, poultry farm- 

 ing, dairying, cattle raising, and other industries, so that one 

 needs to understand something c f these principles if he is to 

 keep in touch with what is being done by the producers of 

 our food and clothing and shelter materials. 



4. Biology related to efficient living. In the third place, it 

 has been observed that much of the unhappiness and weakness 

 and inefficiency of human beings is caused by ignorance of 



