MAKING COVER-GLASS PREPARATIONS 23 
EXERCISE VII ‘ 
MAKING AND STAINING COVER-GLASS PREPARATIONS, 
AND FORMUL& FOR STAINING SOLUTIONS 
32. Work for this exercise. Make 2 cover-glass prepa- 
ations from each of the cultures made in Exercise V and stain 
me of each with alkaline methylene blue and the other with 
‘arbol fuchsin. Describe the appearance of the bacteria and 
nake a drawing of a few individual bacteria from the prepara- 
ions made from the agar culture. 
Preserve a cover-glass preparation mounted in balsam and 
abeled to accompany notes. 
Prepare the staining fluids used in this exercise from the 
ormule given (§ 37). 
Read the paragraphs in the text-books on making and stain- 
ng cover-glass preparations. See references and text-books 
or various staining solutions that are sometimes used. 
33. Making cover-glass preparations. (2) From bouillon 
ultures. Place two clean cover glasses on the tray. With the 
oop remove a drop of the bouillon culture and spread it in a 
hin layer over about two thirds of the surface of the cover 
lasses. One loopful will ordinarily make from 2 to 4 prepara- 
ions. Allow the liquid to dry on the cover glasses in the 
ir and, when dry, fix the bacteria to them by passing 
hem, film upward, three times through the middle of the 
pper half of the gas flame. Each passage (complete circle) 
hould not occupy more than onesecond. After fixing they are 
zady for staining. (6) From cultures on solid media (agar, 
elatin, potato, serum, etc.). Place the cover glasses on the 
‘ay, and on the center of each put a drop of sterile water or 
ouillon. Touch the surface growth of the culture with the 
nd of the needle and then gently rinse it in the liquid on 
1e covers. Spread the liquid on the covers as before. From 
