74 



BACTERIOLOGY. 



and at another time solid, and which can be added to 

 this bouillon without in any way interfering with the 

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

 in, the organisms will be fixed in their positions and 

 the conditions will be analogous to those seen on the bit 

 of potato. 



Fig. 14. 



Plate showing certain macroscopic ctiaracteristics of colonies. Natural size. 



Gelatin possesses this property. At a temperature 

 which does not interfere with the life of the organisms 

 it is quite fluid, whereas when subjected to a lower tem- 

 perature it solidifies. When once solid it may be kept 



