110 CLASSIFICATION AND DESCRIPTION OF BACTERIA 
special staining procedures have been described in the Chapter on 
Staining. Capsulated bacteria usually grow with a sticky, slimy growth 
which when touched with a needle, will pull out into a thread. In 
liquid media the sediment in the bottom of the culture tube will often 
show a slimy appearance. On the ordinary smears stained with aque- 
ous alcoholic solutions of the aniline dyes, the capsulated bacteria 
often show a halo about each cell. This seems to resist the staining 
procedure and may often be made more visible by slightly moving the 
fine adjustment of the microscope. 
Staining Reactions. The theory of staining and the preparation 
of smears has been fully described elsewhere. To make a complete 
study of the staining properties of an organism, all of the stains men- 
tioned on the Descriptive Chart should be used. The common special 
stains, such as the acid-fast, should also be tried. 
Oxygen Relations. The relation to oxygen may be determined 
from the closed arm of the fermentation tubes. Before using, however, 
it is advisable to reduce the dissolved oxygen to a minimum. This 
may be done either by a vacuum pump or boiling. 
The incubation of streak plates by means of Torrey’s method will 
give good results. Also agar streaks of the organism may be incubated 
in a Novy Jar. 
Nutrient Broth. After this medium has been inoculated from a 
young culture of the organism, it should be incubated at the optimum 
temperature for the organism. The characteristics of growth should 
be recorded on the Chart and the culture saved for other tests as here- 
after described. Before these observations are made the tube should 
be shaken as little as possible in order not to destroy any ring or pellicle 
formation. 
Agar Stroke. Streak the agar slant in a straight line from the 
bottom of the slant to the top. Care should be exercised not to cut 
through the surface of the slant.. If the inoculum is deposited 
within the agar when it is intended for the surface anaerobic 
conditions may be established. With freshly prepared agar streaks, 
in the bottom of which is water “of condensation, care must be 
used not to lay them flat on the desk since a spreading growth will 
usually result. 
Agar Colonies. Pour agar plates with a dilution which will allow 
few colonies on the plate. Ten to twenty are sufficient when cultural 
characteristics are to be determined. Spreading colonies should be 
avoided either by inverting the plates during incubation or the use of 
Hill’s porous covers. 
