

BACTERIOLOGICAL TECHNIC. 



39 



Fill a small to medium-sized beaker about two-thirds full of the culture 

 medium. Grasp a plugged tube near the upper end, holding it between 

 thumb and first two fingers of the left hand. Remove the cotton plug by 

 means of the first and second, second and third, or third and fourth fingers of 

 the right hand, grasping the free portion of the plug with the back of the 

 fingers toward the cotton. Holding the tube slightly inclined on a level 

 with the mouth, take beaker with medium in right hand (at the same time 

 holding the cotton plug as described), see that the beak rests lightly upon 

 and projects slightly over the edge of the tube, and pour, at the same time 

 shifting the eyes to the lower end of the tube to watch the filling process. 

 Fill tubes one-third full. Set down the beaker and replace the cotton plug. 

 Place the filled tubes in special wicker baskets, with a little cotton at the 

 bottom to prevent breaking. Some practice is necessary in order to pour 

 so that none of the liquid comes in contact with the upper third of the tube. 

 This must be avoided, in order to prevent the cotton plug from sticking. 

 Tubes may also be filled from funnel with rubber hose, stop-cock, and glass 

 nib attachment. Occasionally it is desirable to place exact amounts of 

 culture media in the tubes, in which case a graduate, a burette, a pipette, or 

 other convenient measuring device may be used. 



FIG. 15. Diagrammatic sectional view of Arnold steam sterilizer illustrating the principle 

 of steam formation, circulation and condensation. 



4. Sterilization of Culture Media. 



All culture media in tubes as above set forth, and the portions remaining 

 after the desired number of tubes are filled, must be considered as being 

 contaminated with living microbes and their spores. These microbes and 

 spores are killed by the sterilizing process. For all ordinary purposes the 



