Microorganisms in Relation to Man 587 



their products? 26. How may bacteria be classified on the basis of 

 their relation to oxygen? 



27. Why is the study of bacteria difficult? 28. What methods 

 are used to make bacteria visible? 29. How are bacteria grown for 

 study ? 30. Why is it necessary to sterilize materials and containers ? 

 31. From what sources may cultures be inoculated to obtain growths 

 of bacteria? 32. What conditions favor their growth? 



33. What is the simplest form of bacteria? 34. What different 

 forms do bacteria take in different conditions? 35. What are the 

 classes of rod-shaped bacteria? 36. Give an example of motile bac-' 

 teria. 37. How do they move? 38. Illustrate their rate of motion. 

 39. Give examples of bent rod-shaped bacteria. 40. Give an example 

 of a pronounced spiral form. Where may it be found? 41. How 

 may the size of bacteria be estimated ? 42. How many of the medium 

 size would equal the thickness of ordinary paper? 43. Compare with 

 these the size of the influenza bacteria. 



44. How do bacteria usually reproduce ? 45. In what other manner 

 do they sometimes reproduce? 46. How rapidly do they multiply? 

 47. What conditions are unfavorable to bacteria ? 48. Where are the 

 greatest numbers found? 49. What forms are found in water under 

 ordinary conditions? 50. When polluted by sewage? 51. What 

 common foods are especially liable to be infected with bacteria ? 



52. How are bacteria affected by drought ? 53. What is the effect 

 of freezing? 54. What is the effect of heat? 55. What temperature 

 kills the harmful bacteria in milk? 56. What bacteria thrive in high 

 temperatures? 57. Where are they useful? 58. What is the effect 

 of cooking on bacteria ? 59. How may the spores be killed ? 60. Why 

 are certain vegetables, as corn, beans, and peas, difficult to can? 

 61. By what method can they be sterilized in the home? 62. What 

 is the effect of light on bacteria? 63. What kind thrives in light? 

 64. What use is made of light in medicine ? 



65. What is the effect of whitewash on some bacteria ? 66. What 

 condition of the soil hinders the beneficial bacteria? 67. How is this 

 corrected? 68. What protection has the stomach against certain 

 bacteria? Why? 69. How is the decay of fruit. begun? 



70. Mention the most familiar and safe substances to preserve food. 

 71. What dangerous preservatives are sometimes used? 72. What 

 germicides are useful in household sanitation ? 73. Name some useful 

 in the body. 74. What is the value of so-called germicidal mouth- 

 washes, tooth pastes, and soaps ? 75. Give instances in which bacteria 

 are helpful to each other. 76. In what ways is the work of micro- 

 organisms necessary to other forms of life ? 



