CHAPTER II. 



GENERAL MORPHOLOGY REPRODUCTION- 

 CHEMICAL AND PHYSICAL PROPERTIES. 



GENERAL MORPHOLOGY. 



Bacteria (sing., Bacterium). In introducing the subject 

 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 instru- 

 ment 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 microbiological 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. Bacteria are studied either in the fresh living 

 condition or when stained by appropriate dyes, especially 

 those derived from coal tar, methylene blue, and fuchsin. 



Bacteria are exceedingly small single cells, in their natural 

 state transparent, colorless, and apparently homogeneous, 

 possessing a very low power of refracting light. They consist 

 (22) 



