142 PATHOGENIC BACTERIA. 
3. Place in the incubator and examine at the 
end of from eighteen to twenty-four hours. 
4. The influenza colonies appear as minute color- 
less, glassy, transparent points, resembling drops 
of dew. ‘They are barely visible to the unpractised 
eye, and require a low magnifying power to be seen 
clearly. 
Fic. 76.—Bacterium influenzz: colonies on blood-agar ; 
low magnifying power (Pfeiffer). 
5. Study the morphology and biology of the 
organisms in one of these colonies. "They should 
not grow on ordinary media, and should have the 
morphology of the influenza bacteria. 
6. Prepare smears from one of the purulent 
