BACILLUS TYPHOSUS 61 



colony, which is more filmy and spreading. The 

 gelatine is not liquefied. A streak sub-culture in 

 gelatine shows exactly the same characters and pro- 

 duces a semi-transparent iridescent growth spread- 

 ing over the surface of the medium with a thin filmy 

 waved margin to be well seen on each side of the 

 growth represented (Fig. 53). 



No gas bubbles are produced when the organism 

 is cultivated in gelatine containing glucose (compare 

 Fig. 61, B. Coli) and milk is not coagulated. 

 Cover glass preparations from such a culture or from 

 similar cultures on agar show organisms like those 

 described in the colonies (Fig. 54). They are, how- 

 ever, often longer than when found in tissues and 

 chains of several apposed cells and long filamentous 

 forms are by no means rare, especially in bouillon 

 culture. The bacilli are, compared with B. Coli, 

 longer, thinner, and less frequently coccoid in form. 



Cultures can be obtained at temperatures ranging 

 from 4° C. — 46° C. The optimum temp, is about 

 37" C, and the] thermal death point of the cell 

 about 60° C. 



On some media, especially potato, the organisms 

 show a tendency to segregation of the protoplasm, 

 so that when stained the extremities of the cell 

 are deeply coloured and the centre is clear and 



