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 motility 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 slide, 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 



