TEST-TUBE, STAB- AND SMEAR-CULTURES. 137 



Cultures of this form are not only useful as a means 

 of preserving the different organisms with which we 

 may be working, but serve also to bring out certain 



FIG. 34. 



Series of stab-cultures in gelatin, showing modes of growth of different 

 species of bacteria. 



characteristics of different organisms when grown in 

 this way. 



If gelatin be employed and the organism which has 

 been introduced into it possesses the power of bringing 



