44 



GENERAL BACTERIOLOGY 



d. Examine the thinner layers, noticing the arrangement of cells 

 with reference to each other, and draw a sufficient number to illus- 

 trate this relationship. 



Hanging-Drop Preparations. 



a. Make hanging-drop preparations from bouillon cultures pre- 

 pared above (22) and also from those supplied. 



&. Examine with oil-immersion objective and assign organisms 

 to their proper places, as determined by cell grouping, in the foUow- 

 , ing scheme : 



Agar Hanging-Drop Cultures (Wesbrook). 

 a. Melt a tube of a'gar and cool to 43° C. 



h. Sterilize a cover-glass by passing it two or three times through 

 the flame quickly. 



c. With the needle make a streak on the cover glass about 3 mm. 

 long of B. subtilis. 



