CHAPTER IX. 
THE MICROSCOPIC AND CULTURAL STUDY OF 
BACTERIA. 
Methods for the Microscopic Study of i F. Differential Stains for Bac- 
Bacteria. teria. 
I. Living Bacteria. 
A. Hanging Drop. 
B. Hanging Block. 
C. Dark-field Illumination. 
D. Intra-vitam Staining. 
1. Gram. 
2. Ziehl-Neelsen. 
3. Gabbett. 
4. Polychrome Stains. 
5. Smith Sputum Stain. 
II. Staining of Bacteria. ; m. Staining Bacteria in Tissues. 
IV. Methods and Media for the Cul- 
tivation OF Bacteria. 
A. Chemistry of Stains 
B. Preparation of Stains. 
C. Techniqueof Staining Bacteria. 
D. Intensive Stains for Bacteria. [ V. Cultivation of Bacteria. 
E. Stains for Special Structures ^- Inoculation of Cultures. 
of the Bacterial Cell. 2. Isolation of Pure Cultures. 
1. Spores. 
2. Capsules. 
3. Polar Bodies. 
4. Flagella. | 
3. Incubation of Cultures. 
VI. Study of Bacterial Cultures. 
METHODS FOR THE MICROSCOPIC STUDY OF BACTERIA. 
Bacteria may be examined directly under the higher powers of 
the microscope for their morphology, motility, arrangement, method 
of reproduction, and their behavior in specific sera, or they may be 
stained with various anilin dyes and chemicals to bring out details 
of structure or composition, and their relation to various tissues in 
pathological processes. 
Glass slides and cover-glasses are conveniently used for this purpose. 
IVIicroscopic slides should be made from clear, colorless glass. Cover- 
glasses should be made of thin glass. The available working distance 
of oil-immersion lenses is somewhat less than L5 mm., consequently 
cover-glasses should not measure more than 1 mm. in thickness as a 
maximum limit. Xo. 1 cover-glasses are suitable for bacteriological 
work. 
Glass slides and cover-glasses are best cleaned in a mixture of 
potassium bichromate, 1 part; water, 4 parts; sulphuric acid, () parts. 
The bichromate is dissolved in the water with the aid of heat and 
cooled; the acid is added slowly with constant stirring. Immersion 
in this mixture for twenty-four hours removes dirt and grease from 
both slides and cover-glasses. The cleansed glassware is removed 
from the cleansing bath and washed with running water until neutral 
to litmus paper. It is stored either in slightly ammoniacal alcohol, 
or dried with a soft cloth, previously freed from grease by boiling in 
a 5 per cent sodium carbonate solution, 
