very difficult. Luckily, the emperor Alexander ordered his governors and 

 generals to send natural objects from all regions, to please his old teacher 

 Aristotle. 



As people traveled more widely and saw more and more kinds of living 

 things, they naturally changed their ideas about life. For one who moves 

 about must broaden his outlook upon the world. He comes to see his fel- 

 lows and the other inhabitants of the earth in a different way from one who 

 lives always in the same neck of the woods or along the same stretch 

 of shore. 



As time goes on, we move about and see larger regions of the world and 

 more of its inhabitants. Wherever strangers meet, knowledge increases: 

 we learn from each other. We thus lengthen our lists of known plants and 

 animals and find new uses for various kinds. The Spanish missionaries 

 brought Peruvian bark to Europe; and for over three centuries that was the 

 only remedy we had for malaria. People formerly threw to the dogs por- 

 tions of food animals which we now know to be worth more to us than the 

 meat itself. A few very old men and women remember when the tomato 

 was considered a poisonous fruit. The weeds and vermin of one region are 

 valued and cultivated in another. 



Men migrating to new regions often found new pests attacking their 

 crops or their cattle. And they often met new diseases too. As population 

 grows, we have to make farms yield more. Growing cities create problems 

 of water supply and ventilation, sanitation and the transporting of food, 

 which is always in danger of spoiling. New chemicals and smokes and 

 dusts in new industries bring new problems of protecting the health of 

 workers. 



Today, when planes encircle the globe in a few days, or survey inacces- 

 sible mountain valleys, or bring together on short notice representatives of 

 widely scattered peoples, biology means more than ever. Plants and animals 

 of any region come to be important to people far away. Human life every- 

 where may profit from whatever people anywhere can get out of biology, 

 whether it is a substitute for quinin or an antitoxin, a new sulfa drug or a 

 new idea about managing things. And flying itself is possible for more 

 people only as special biological problems are solved. 



Modern biology, or life science, is thus one of the outcomes of the great 

 social, economic, and political changes of the past three or four centuries. 

 And in turn biology is bringing about still further changes — many of them 

 no doubt improvements in our ways of living. 



Kinds of Biology We can ask many different questions about any 

 given subject. Among the first questions that each of us probably asked 

 after we learned to speak are those that have to do with class, or kind. 

 What kind of tree is that? What kind of stone is that? And the usual 



