104: LABORATORY EXERCISES. 



air, the dirt, and the water, and those 

 which have not been exposed? 



2. Draw a figure of the dish you are studying, 



representing carefully the form and size 

 of the spots (colonies of bacteria or 

 mould) . 



3. Study the same dish several days later. 



Make a careful drawing as in 2 above. 

 Have the colonies changed in size or ap- 

 pearance since your last study? 



4. Describe the color of the colonies. 



5. Do any of the colonies appear to affect the 



agar around them? (Smell of the agar.) 

 D. Microscopic study of bacteria. 



Carefully lift the cover from one of the plates 

 of agar which has been exposed. Touch one 

 of the colonies of bacteria with the point of a 

 needle, and then rub the needle-point on a 

 clean glass slide; add a drop of water to the 

 spot touched by the needle, and cover with a 

 cover-glass. Examine with the highest powers 

 of the microscope. 



1. What is the color of the tiny bodies (bac- 



teria) which you see? 



2. Do you find more than one kind of bacteria ? 



If so, what is the shape of each ? 



3. Do any of the bacteria seem to be in mo- 



tion? 



4. Place a drop of stain (eosin, carbol fuchsin, 



or LoefHer's blue) at the side of the cover- 

 glass and allow it to run beneath the 

 glass, staining the cells. Can you make 



