PLATE CULTURES. 67 
‘colonies’? in distinction from ‘cultures’ to be 
determined. 
1. Liquefy three gelatin- or agar-tubes! by placing 
in a water-bath. Gelatin-tubes must not be heated 
above 40° C. Agar-tubes may be heated to 100° 
C., but-must be cooled to 40° C. before the inocu- 
lations are made. 
2. With a sterile platinum needle transfer a 
Fic. 42.—Petri dish with colonies. 
minute portion of a culture to the liquefied medium 
in the first tube. 
3. Shake the tube thoroughly without producing 
bubbles in the medium, and transfer a loopful to the 
second liquefied tube. 
4. Shake the second tube, and transfer a loopful 
to the third tube. 
1 Bouillon-tubes or tubes of sterile water may be substi- 
tuted for the first two gelatin- or agar-tubes when it is 
desired to make but one plate, 
