GENERAL BACTERIOLOGY 71 



contents into a sterile petri dish, carefully lifting the 

 cover (Fig. 26) and quickly replacing it. 



4. Repeat this operation with the other tubes, 

 excepting glucose agar. 



S- Place all petri dishes containing the liquid agar 

 on a level surface. 



6. When the agar has solidified, expose, by removing 

 the cover, one dish of pld;in agar and one of wort agar 

 to the air of the laboratory, and the other two outside 

 on the window-sill, for 5 minutes. 



7. Replace the cover and place in incubator. 



Fig. 26 

 Pouring Medium into Petri Dish 



8. Cool the water bath to 43° C, and mix the 

 scrapings from under a finger nail with the liquid 

 glucose agar. Incubate at 37° C. 



9. Remove the plug of a tube of broth and place a 

 hair in the liquid. Incubate at 37° C. 



Liquefied agar media should be inoculated at a 

 temperature no higher than 43° C. nor lower than 40° C. 

 Above 43° C. the organisms are liable to be injured 

 by heat; below 40° C. the agar solidifies, and an even 

 distribution is impossible. If gelatin is used, the 

 latter precaution is not imperative, as gelatin solidifies 

 at about 25° C. 



Observe and make notes on the appearance of these 

 petri dishes after 24 hours. By this time it wiU bp 



