BACILLUS TYPHOSUS. 405 



the ordinary methods of staining. (See Staining of 

 Flagella, page 205.) 



Biological Characters. The typhoid bacillus is a 

 motile, aerobic, non-liquefying bacillus, developing 

 best at 37 C.; over 40 and below 30 its growth is 

 retarded; below 10 it ceases. It grows most abun- 

 dantly in the presence of oxygen, but oxygen is not 

 essential to its development. 



Its growth on most culture media is similar to that 

 of the bacillus coli conimunis, but it is somewhat 

 slower and not quite so luxuriant. 



FIG. 52. 



A superficial and a deep colony of typhoid bacilli in gelatin. 

 X 50 diameters. 



Growth on Gelatin Plates. (Fig. 52.) The colonies 

 growing deep down in this plate medium have nothing 

 in their appearance to distinguish them; they appear 

 as round points with a -sharp margin, of a yellowish- 



