370 



TYPHOID FEVER 



media growths of the b. typhosus appear less dense than those 

 of the b. coli. Stab cultures in peptone gelatin give a somewhat 

 characteristic appearance. On the surface of the medium growth 

 spreads outwards from the puncture as a thin leaf-like film or 

 pellicle, with irregularly wavy margin (Fig. 113, A). It is semi- 

 transparent and of bluish-white colour. Ultimately this surface 

 growth may reach the wall of the tube. Not infrequently, how- 

 ever, the surface growth is not well marked. Along the stab 



FIG. 112. Typhoid bacilli, from a young culture on agar, .showing 



flagella. See also Plate III., Fig. 20. 

 Stained by Van Ermengem's method, x 1000. 



there is an opaque whitish line of growth, of finely nodose ap- 

 pearance. There is no liquefaction of the medium, and no 

 formation of gas. In stroke cultures there is a thin bluish- 

 white film, but. it does not spread to such an extent as in the 

 case of the surface growth of a stab culture (Fig. 113, B). In 

 gelatin plates also the superficial and deep colonies present 

 corresponding differences. The former are delicate semi-trans- 

 parent films, with wavy margin, and are much larger than the 

 colonies in the substance, which appear as small round points 



