TEST-TUBE, STAB AND SMEAR CULTURES 169 



liquefaction i. e., of digesting it it will soon be discovered 

 that the mode of liquefaction differs with different organ- 

 isms and is practically constant for the same organism. 



FIG. 32 



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

 species of bacteria. 



Some bacteria cause a liquefaction which spreads across the 

 whole upper surface of the gelatin and continues gradually 

 downward; with others it occurs in a funnel-shape, the 

 broad end of the funnel being uppermost and the point down- 



