30 LABORATORY BACTERIOLOGY 
their appearance. The notes should contain a detailed record 
of the cultures made in this exercise. 
Read carefully the paragraphs in the text-books on making 
plate and roll cultures. 
43. Making agar plate cultures. Take 3 large tubes of 
agar, stand them in a water bath, and boil until the agar is 
liquefied. Then cool by standing the tubes with a thermome- 
ter in a cup of water at a temperature of about 50°C. As the 
temperature rises, add a little cold water. When the tempera- 
ture of the agar reaches that of the water, and the temperature 
of the whole has lowered to 40° C., the agar is ready for use. 
For convenience in labeling, number the tubes 1, 2, and 3. 
Place 3 sterilized Petri dishes on the leveling tripod and 
adjust it by means of a spirit level. With the wire loop pro- 
ceed by the same method as followed in making bouillon 
cultures. Take one loopful of the bouillon culture, place it 
in agar tube 1 and mix by carefully shaking. Flame the 
wire and transfer 2 loopfuls of agar from tube 1 to tube 2 
and mix as before. Again flame the loop and transfer 3 loop- 
fuls from tube 2 to tube 3 and mix as with tubes 1 and 2. 
After the tubes are inoculated, pour the agar into the Petri 
dishes. In doing this remove the plug, carefully flame the 
mouth of the tube, and after quickly cooling, raise with the 
left hand the edge of the cover on one side of the Petri dish 
sufficiently to allow of inserting the mouth of the tube. After 
the agar is poured out of the tube replace the cover immedi- 
ately. Label and number the Petri dishes to correspond with 
the dilutions in the tubes: thus, plate 1 is from tube 1, plate 2 
is from tube 2, and plate 3 is from tube 3. Place the label 
near the edge of the cover.. The Faber pencil for marking 
glass may be used instead of the gummed label. In making 
the dilutions it is important that the wire loop should be 
flamed after making each transfer. 
44. Making gelatin plate cultures. These are prepared 
precisely as the agar plates, with these exceptions: (1) the 
