38 LIFE DEPENDS ON ADAPTATIONS 



transportation and refrigeration. We have learned to 

 control disease so well that we have increased the number 

 of years man can live. In other words, man is a thinking 

 animal and as such has learned to control and improve 

 his environment. 



How We Make Adaptations. Have you learned to 

 swim? You soon will if you have not already done so. 

 You may remember how hard it was at first to keep your 

 head above water and not to be frightened. You found 

 that as you learned the different motions, you gradually 

 improved, and then all at once you were able to swim. 

 You will never lose this adaptation so long as you live. 

 You have mastered this problem. When any one has 

 completely mastered anything, like learning to swim, 

 skate, read, or write, he has made an adaptation. So in 

 this book we have given you a number of helps so that 

 when you finish a unit of work, you may be sure that you 

 have complete mastery of the subject. You have, for 

 example, at the end of each problem, self -testing exercises 

 which will help you find out if you have mastered the 

 information in the pages just preceding. If you cannot 

 fill in the blanks correctly, you should study those facts 

 in the problem that you do not remember and then try the 

 test again. Keep at it until you have mastered the prob- 

 lem. Then there are other tests which help you apply 

 the information you have gained. You may know all 

 the facts in the unit, but if you cannot apply these facts 

 in the solving of simple problems, then you will not get 

 very far in the mastery of the subject. Let us try to use 

 these helps to gain the mastery which means success. 



SELF-TESTING EXERCISE 



Select from the following list those words which best fill the blank 

 spaces in the sentences below and arrange the words in proper numer- 

 ical order. A word may be used more than once. 



