MOUNTING OF BACTERIAL CULTURES 



89 



be pushed a little way into the tube and a few drops of 

 melted paraffin dropped on the top of the wool, or the plugs 

 should be covered either by indiarubber caps or by pieces of 

 sheet rubber tied over them. These caps should be previously 



FIG. 39. Hearson's incubator for use at 37 C. 



sterilised in 1-1000 corrosive sublimate and then dried. Before 

 they are placed on the tube the cotton-wool plug ought to be 

 well singed in a name. "Cool" incubators are often used for 

 incubating gelatin at 21 to 22 C. An incubator of this kind 

 fitted with a low-temperature Hearson's regulator is in the 

 market. 



Method of Mounting Bacterial Cultures as Permanent 

 Museum Specimens (Richard Muir). (a) Stab or Stroke 

 Cultures in Nutrient Gelatin or A gar Media. When the culture 

 shows typical characters, further growth is arrested by placing the 

 tube in a formol vapour chamber, or by saturating the cotton- 

 wool plug with strong formalin. Then leave for a day or two. 

 Make up the following : 



(1) Thymol water (saturated in cold) . . . 100 c.c. 



Glycerin . . . . . . . 20 c.c. 



Acetate of potash ...... 5 grms. 



Coignet's (gold label) gelatin .... 10 grms. 



Render the mixture acid to litmus with acetic acid ; clear with white 

 of egg and filter. 



