BACILLUS TYPHOSUS. 405 
the ordinary methods of staining. (See Staining of 
Flagella, page 205.) 
Biological Characters. The typhoid bacillus is a 
motile, aérobic, 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 communis, but it is somewhat 
slower and not quite so luxuriant. 
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- 
