CHAPTER X. 



THE MICROSCOPIC EXAMINATION OF BACTERIA AND 

 STAINS EMPLOYED. 



The examination of bacteria from cultures. Because of 

 "the minute size of bacteria it is necessary in the study of 

 their morphology to use a compound microscope with the 

 high power (oil immersion) objective and substage con- 

 denser. The successful study of bacteria therefore requires 

 one to be familiar with the use of the microscope.* 



Bacteria are examined microscopically in the living, 

 unstained condition and in fixed and stained preparations. 



In the fresh state they are examined in what is known as 

 hanging drop preparations. These are prepared from liquid 

 and solid media cultures. 



(a) From a bouillon culture. Place a clean cover-glass 

 on a tray. With the platinum loop Remove a drop of the 

 liquid culture and place it on the middle of the cover-glass. 

 With a pair of fine forceps invert the cover-glass over the 

 glass ring fixed to a slide for this purpose. The surface of 

 the ring should previously be moistened with liquid vaseline 

 to prevent the cover-glass from sliding and to keep the 

 preparation from drying out. Examine with the oil immer- 

 sion objective. 



(6) From cultures on solid media. On account of 

 the very large number of bacteria in the growth on solid 

 media it is necessary to separate them in a clear liquid. This 

 is done by taking a cover glass as before and placing a loop- 

 ful of bouillon or sterilized water on the center. Touch the 

 surface growth very gently with the end of the platinum 



* A course in microscopy or in the technique of the microscope 

 should precede the study of bacteriology. Those who are obliged to 

 acquire this knowledge outside of regular instruction in the subject 

 rare referred to "The Microscope" by S. H. Gage, Comstock Publish- 

 ing Company, Ithaca, N. Y. 



