CHAPTER II. 



GENERAL MORPHOLOGY REPRODUCTION- 

 CHEMICAL AND PHYSICAL PROPERTIES. 



GENERAL MORPHOLOGY. 



Bacteria (sing., Bacterium). In introducing the sub- 

 ject of morphology a few words as to the technic of 

 observing bacteria will not be amiss. The compound 

 microscope is necessary to all microbiological work. 

 Since this book is devoted to principles, a detailed 

 description of the instrument and its operations would 

 be foreign. Let it suffice to say that the compound 

 microscope is a series of finely ground lenses by which 

 exact pictures in definite magnification can be obtained. 

 An object to be examined is placed upon a glass slide 

 and covered with another but much thinner glass cover. 

 This is laid upon the table of the instrument and the 

 tube holding the lens placed at a proper distance to 

 obtain the best light and clearest picture when viewed 

 through the eye-piece end. For nearly all microbiologi- 

 cal observations it is necessary to use a special lens of 

 high magnifying power, called an oil-immersion lens, 

 and to introduce between the lens and the object glass 

 a drop of pure cedar oil into which the lens front dips; 

 this concentrates and filters the light. The microscope 

 is also used to examine the colonies of bacteria. Bac- 

 teria are studied either in the fresh living condition 



