PROBLEM I . Houi) We Are Protected Against Micro or {yanisms 3 1 9 



8. Do external conditions affect the growth of bacteria? Devise and 

 perform an experiment to discover the effect of different temperatures 

 (ice box, close to a furnace, room temperature, etc.) on growth of bac- 

 teria. Will you need a control? Does boiling kill bacteria? How could 

 you find out? Are vou sure your method is a good one? Devise and per- 

 form an experiment to find the effect of drying on the growth of bacteria. 



9. What do you remember about the blood? Answer these questions: 

 {a) Can red corpuscles serve as scavengers? Why or why not? {b) When 

 a doctor wishes to know whether there is an internal infection he ex- 

 amines a drop of blood under the microscope. What is he looking for? 

 How will he make his decision? 



10. Can you explain how a scientist would perform an experiment to 

 discover whether an antibody is specific? (He would use rabbits or 

 guinea pigs, probably.) Give all the steps in order. Would he need a 

 control? 



1 1 . Do you think the people of India and China were wise to expose 

 their children to disease when a mild form occurred? Explain. Explain 

 why you would or would not recommend this to your family. 



12. Make an outline summary of this problem. 



Further Activities in Biology 



r. If you can obtain pus material from a small pimple, smear a bit 

 of it on a slide and allow it to dry. Then pass the slide through a flame 

 quickly once or twice. (Do not bring the material in direct contact with 

 the flame.) Now cover the dried pus with a dye such as methylene blue, 

 and allow it to stand for two or three minutes. Wash the dye off in 

 running water; examine the shde under the high power of the microscope. 

 You should be able to see phagocytes with engulfed bacteria. 



2. Read about Eli Metchnikoff and his discovery of phagocytes. {Mi- 

 crobe Himters by Paul De Kruif.) 



