WHAT IS BIOLOGY? 9 



the utmost value from what we finally carry around with us in 

 the way of ideas about plants and animals there should be some 

 systematic study. You might go out and gather up all the 

 samples of plants and animals you come across, and start sorting 

 them. Or you might use a magnifying glass and discover in 

 every sample many things that you would otherwise never have 

 found out. Or you might cut your samples open and find out 

 something about their internal organs, and perhaps guess at 

 what makes them go. Or you might sit still and watch what is 

 going on in the ground, in the water, in the air, and make note 

 of what you see and hear. You might take your samples into 

 the laboratory and test them to find out what kinds of material 

 enter into their composition, or what changes they bring about 

 in the materials they take in. Or you might experiment with 

 them to find out what makes them do the many queer things. 



All the methods of classification, observation, and experimen- 

 tation may be used on all living things. But we do not have to 

 do all these things for every animal and plant. Indeed, we 

 shall find these methods very slow, even if we confine ourselves 

 to the study of only a single kind of life form. We shall have 

 to get a very large part of our knowledge at second hand, by be- 

 ing told what others have found out before us, through conversa- 

 tions, through lectures, through reading, through pictures. Yet, 

 no matter how much we may get out of books, it is well to 

 remember that all useful knowledge originates in the observa- 

 tions and experiences and experiments of people like ourselves. 

 Whether we use our naked eyes or have the assistance of micro- 

 scopes and telescopes, whether we taste and smell bits of plants 

 and animals or make use of chemicals, whether we merely 

 pull a lizard's tail to see what he will do or develop long and 

 complicated experiments, the source of all biological knowledge 

 is in the plants and animals themselves and not in books. 



7. What living things do. All living things, even plants, 

 are constantly doing something that brings about changes in 

 the world. Some of these activities are very rapid, or sudden, 

 or dramatic : a hawk swoops down and carries off a fowl, or an 



