22 LIVING THINGS AND THE ENVIRONMENT 



of all kinds in a town or city have to be disposed of. Houses 

 have come to be placed close together, or piled one on top of another, 

 as in modern apartment buildings. Fields and trees, in fact most 

 aspects of country outdoor life have virtually disappeared in a 

 large city. City-dwelling man has come to live in an artificial 

 environment. 



Care and Improvement of One's Environment. — Man can 

 modify or change his surroundings by making this artificial envi- 

 ronment favorable to live in. He can heat his dwellings in winter 

 and cool them in summer so as to maintain a moderate and nearly 

 constant temperature. He can see that his dwellings have win- 

 dows to let light and air pass in and out. He can have light at 

 night and shade from intense light by day. He can have a sys- 

 tem of pure water supply and drains or sewers to carry awaj^ 

 his wastes. He can plan parks and playgrounds so that the city 

 folk may have breathing spaces, as do their more fortunate neigh- 

 bors in the smaller towns. He can see to it that people ill with 

 *' catching " or communicable diseases are isolated or quarantined 

 from others. Best of all, he is slowly learning to control the harm 

 done by the tiny parasites, plant and animal, that cause and spread 

 diseases. This care of the artificial environment is known as sani- 

 tation, while the care of the individual for himself within the envi- 

 ronment is known as hygiene. It will be the chief aim of this book 

 to show girls and boys how they may become good citizens through 

 the proper control of personal hygiene and sanitation. 



Summary. — We have found the life activities to be reactions 

 to stimuli. As a result, plants and animals show definite responses 

 that are called tropisms, and it appears that by means of these 

 tropisms living things are better able to succeed in the world. 

 They are, in a sense, creatures of the environment, for the sur- 

 roundings determine the types which can live in any particular 

 place. Plants and animals are also fitted or adapted to live in 

 certain conditions by having their parts modified or changed so 

 as to fit better the conditions in which they live. Man, how- 

 ever, is able to change the conditions of his environment, or else to 

 move to a more favorable one. In this sense, he is the most adapt- 

 able of all living creatures, and as such, controls his living con- 

 ditions. 



