TUBE CULTURES 



225 



4. Label the newly planted tube and incubate. 



NOTE. When gelatine is stored for some time the upper 

 surface of the cylinder becomes concave owing to evaporation. 

 Tubes showing this appearance should be liquefied and again 

 allowed to set before use for stab culture, otherwise when the 

 needle enters the medium, the surface tension will cause the 

 gelatine cylinder to % split. 



FIG. 118. Sloped or slant- 

 ed medium for streak or 

 smear culture. 



FIG. 119. Straight tube. 



Shake Culture. 



1. Liquefy a tube of nutrient gelatine (or agar, or 

 other similar medium), by heating in a water-bath 

 (Fig. 121). 



2. Inoculate the liquefied medium and label it, etc., 

 precisely as if dealing with a tube of bouillon. 



15 



