GENERAL BACTERIOLOGY 75 



Inoculations from liquid media are made with the 

 looped needle. This may also be used from a solid 

 medium, if a considerable amount of growth is required. 

 The contents of the loop are then spread over the whole 

 surface. 



EXERCISE 3 



Describe the appearance of the colonies as outlined 

 in Section 9. 



EXERCISE 4 



Examine as to motiUty in the hanging drop. 

 Preparation of a hanging drop (Fig. 28): 



1. Clean a cover slip in alcohol. Pass several 

 times through the flame so as to burn the last traces of 

 grease off the surface. 



2. Place a loopful of pure water on the center of the 

 cover slip. 



3. Flame the straight platinum needle, and, after 

 cooling, touch one of .the colonies- and mix lightly with 

 the drop of water without spreading it. Take only a 

 minute amount of culture, so as to produce a faint 

 cloudiness in the water. 



4. Smear vaselin around the depression in a hollow- 

 ground shde, invert the cover slip over the depression, 

 and gently press the margin on the vaselin. 



5. Examine in oil, using very little light, 



EXERCISE 5 



Molecular movement. — Rub a small amount of car- 

 min in a mortar with some water and make a hanging- 

 drop preparation. When examining this through the 

 oil-immersion lens, it will be observed that the small 



