CULTURAL TECHNIQUE 



11 



GELATIN 

 1 PER CENT LACTOSE 

 + 155 IO/I6/08 

 INTERMITTENT. 



closing the apparatus the vent must be left open until the 

 air is completely expelled by the generating steam, which 

 should issue freely. In a mixture of air and steam the tem- 

 perature does not correspond to the pressure noted. Five 

 pounds of steam pressure produces a temperature of 109 C. ; 

 10 pounds, 115 C.; 15 pounds, 121 C. In all cases the 

 apparatus must be allowed to 

 cool off slowly and the vent 

 opened very slightly ; other- 

 wise the pressure will de- 

 crease more rapidly than the 

 temperature of the media. 

 This will cause the media to 

 boil so violently that the plugs 

 may be forced from the con- 

 tainers and a portion of the 

 media lost. This is especially 

 true in the case of media in 

 flasks. Media in tubes should 

 be heated to 120 C. (15 

 pounds pressure) for five min- 

 utes ; in flasks the time must 

 be extended. 



Care Of media. If possible FlG - 6 - FORM OF LABEL FOR MEDIA 



the media should all be placed In each basket, of media should be 



; placed a slip stating kind of medium, 



111 tubes at the time it IS pre- reaction, date of preparation, and 

 pared, and thus avoid the manner of sterilization 



changes due to prolonged and repeated heating in the succes- 

 sive sterilizations necessary when the media is first sterilized 

 in bulk and again when placed in tubes. After sterilization 

 the media should be kept at room temperature for several 

 days and examined from day to day. If any " specks " in 



