FOR WAGGONER’S BIOLOGY 
41 
glass rapidly through a Bunsen flame three times. This flame will 
kill and “ fix ” the bacteria. Next place a drop of gentian violet 
stain upon the cover glass. (A concentrated solution of purple 
aniline dye and denatured alcohol has been used as a stain with 
satisfactory results.) Let the cover glass stand for a few minutes. 
Then wash by allowing gently flowing water to pass over the 
cover glass. After this place the cover glass, bacteria side down, 
upon a clean slide. 
2. Repeat the process, using a scraping from the teeth which is 
mixed with a drop of water. 
III. The instructor will mount the prepared slides under the 
high power of the microscope. When this has been done you may 
study them. How many shapes of bacteria do you find in each 
case? Do these vary in size? Compare the dimensions of the 
bacteria to the diameter of a hair which has been placed under the 
cover glass. Why are the bacteria seen more easily in the stained 
slides than in the unstained ones? Make drawings of the various 
types and sizes of bacteria which you see. (See Waggoner, Figs. 
127 and 128.) 
IV. What are evidences of the presence of bacteria in any sub¬ 
stance? 
EXERCISE 44 
INTERRELATIONS OF THE ORGANISMS 
OF A HAY INFUSION 
I. Preparation. Use timothy hay (dried) and water from a 
pond. Cut the hay into small pieces and allow a handful of it to 
soak for a few days in a quart of the pond water. Keep the infu¬ 
sion in a warm room. 
II. Study of Organisms in the Infusion. Study samples of the 
water which have been mounted under the microscope. Do this 
two or three times each week. Note the character of any living 
organisms which may be visible. Note the changes which take 
