LABORATORY TECH NIC 43 



all pathogenic bacteria develop best at this tempera- 

 ture. The bacteria of the soil and water probably 

 grow best at about 70 F. or 20 C. After these tubes 

 and plates have been "incubated" for twenty-four or 

 forty-eight hours the bacteriologist observes them 



FIG. 13. Method of transferring cultures from one tube to another. 

 (Hiss and Zinsser.) 



and takes note of the evidences of growth. He will 

 make stained preparations for microscopic observation 

 and note the morphology of the plant. Many stains are 

 in use for demonstrating various characteristics. He 

 will also prepare what is known as a " hanging drop." 

 This consists of a drop of fluid broth culture upon a 



