104 METHODS OF OBSERVING BACTERIA 



19. What is meant by exactly and evenly centred objectives? 



20. Give in detail the steps in the examination of a stained bacterial cover- 

 glass preparation with the microscope. 



21. Give the steps in using the microscope when examining a hanging-drop 

 preparation. 



22. How can the size of bacteria be measured? 



23. What is (a) stage micrometer? (6) eyepiece or ocular micrometer? 



24. Describe the use of these microscopic accessories in measuring bacteria. 



25. What is a camera lucida? What is a photomicrographic camera? 



26. What is a dark-field illuminator? 



27. How does the microscopic image look when a dark field illuminator is 

 used? 



28. Describe the use of the dark -field illuminator. 



29. What is a platinum rod? 



30. What is a concave slide? 



31. What is a Stewart forceps? 



32. Describe the method of cleaning slides and cover glasses. 



33. Describe the method of preparing a hanging drop in a concave slide. 



