METHODS OF ISOLATION. 



99 



possesses the property of being at one time fluid and 

 at another time solid, and which could be added to 

 this bouillon without in any way interfering with the 

 life-functions of the bacteria, then, as solidification set 

 in, the organisms would be fixed in their positions, and 

 the conditions would be analogous to those seen on the 

 bit of potato. 



FIG. 14. 



Showing certain macroscopic characteristics of colonies. Natural size. 



Gelatin possesses this property, and it was, therefore, 

 used. At a temperature which does not interfere with 

 the life of the organisms it is quite fluid, whereas when 

 subjected to a lower temperature it solidifies. When 



