90 LABORATORY AND FIELD EXERCISES 



c. Draw the colonies of one culture dish, indicating their 



distribution, size, and form. 



d. Conclusions. State your conclusions concerning the 



following points : 



(1) How do you account for the difference in the growth 



of bacterial colonies in the two culture dishes 

 exposed to the air in the two different situations ? 



(2) How are bacteria evidently distributed? "Why should 



one avoid crowded rooms in time of disease 

 epidemics ? 



(3) How do you account for the differences in the 



appearance of different bacterial colonies ? 

 2. Expose a sterile liquid culture medium in a test tube to 

 the air as in the first experiment. Observe for several 

 days at successive class exercises. Note any changes 

 in the fluid which appear from day to day. 



MICROSCOPICAL EXAMINATION OF BACTEKIA 



1. Remove a small portion of a colony from one of the cul- 



ture dishes in experiment 1 to a drop of water on a 

 glass slide and cover. 



2. Prepare a similar slide from the liquid culture in 



experiment 2. 



3. Observe these preparations first with a low power and 



then under the high power of a compound microscope. 



a. Form types of bacteria. Consult the text figures and 

 discussions and observe as many of these forms of 

 bacteria as you can find in your preparations. Do you 

 find coccus, bacillus, and spirilla form types ? Note 

 the great variation in form and size of the bacteria, 



I. M<'<-iin'iitx. Do you find bacteria with independent 

 powers of movement?. What is the nature of this 

 movement ? The motor organs, cilia or tiagella, can 



