26 MORPHOLOGY OF BACTERIA. 
(6) Prepare a stain as follows : 
Alum (saturated aqueous solu- 
tiow), IO C.C.5 
Gentian-violet (saturated alco- 
holic solution), 2.0. 
The stain will keep two or three days. 
(c) On an absolutely clean cover-glass' place a 
drop of distilled water. 
(Z) With a sterile platinum needle add to the 
drop of water, without stirring, a very small por- 
tion of an actively motile culture. 
(e) Stand on a water-bath at 60° C. for one-half 
hour. 
(f) Treat the film with the cold mordant for 
twenty-four hours, or with hot mordant (steaming, 
but not boiling) for three minutes. 
(g) Wash thoroughly in running water and dry. 
(2) Treat with the stain the same as directed 
for the mordant. 
(¢) Wash, dry, mount, and examine with the oil- 
immersion lens. 
2. Modification of Pitfield’s Method. 
(a) Prepare solution A as follows : 
Alum (saturated aqueous solu- 
tion), TO Gc, * 
Gentian-violet (saturated alco- 
holic solution), -" Tee 
’ See footnote, page 14. 
