CHARACTERS OF CULTURES. 



323 



a somewhat characteristic 

 appearance. On the sur- 

 face of the medium growth 

 spreads outwards from the 

 puncture as a thin film or 

 peUicle, with irregularly 

 wavy margin (Fig. 116, A). 

 It is semi-transparent and 

 of a bluish-white colour. 

 Ultimately this surface 

 growth may reach the wall 

 of the tube. Not infre- 

 quently, however, the sur- 

 face growth is not well 

 marked. Along the stab 

 there is an opaque whitish 

 line of growth, of finely 

 nodose appearance. There 

 is no liquefaction of the . c u , A'°' ^l^', ,. ■„ ■ 



^ A. Stab-culture of the typhoid bacillus in gelatin, 



medium, and no formation five days' growth. 



^ ^ , ' B. Stroke-culture of the typhoid bacillus on gela- 



ot gas. In stroke-cultures tin, six days' growth. 



*-U^^^ ,"r. « 4-1,;^ 1,1,.;.,U „ T,;4-^ C, Stab-culture of the bacillus coH in gelatin, nine f 



there is a thm bluish-whlte days- growth-, the gela.m is split in its lowe; part , 



film, but it does not spread °"'"s to the formation, of gas. 



to such an extent as in the case of the surface growth of a ' 



staVculture (Fig. 116, B). In gelatin plates also the superficial' 



and deep colonies present cor- ' 



responding 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 r 

 (Fig. 117). These appearances, 

 which are well seen on the third 

 or fourth day, resemble those 

 * seen in agar plates, as already 



described in the method of 

 Fig. 117. — Colonies of the typhoid bad!- isolation; but On gelatin the 



lus (one superficial and three deep) in a gurface colonies are rather 



gelatin plate. Three days' growth at room 

 temperature. X 15. 



more transparent than those on 



