PATHOGENIC BACTERIA. 117 



'form.- Ovalx;occi they were at first called, but they are now 

 known to be rod-shaped, being somewhat longer than broad ; 

 varying, however, much in size and shape. Usually found in 

 pairs, sometimes in filaments of three and four elements. In 

 the material from the body a capsule surrounds each rod. In 

 the artificial cultures this is not found. 



FIG. 64. 



Bacillus of pneumonia in blood of rabbit 1000 X- (Frankel and Pfeiffer.) 



Properties. They are without self-movement ; do not liquefy 

 gelatine. 



Growth. Grow only at high temperature, 35 C. ; are facul- 

 tative anaerobic. The culture me'dia must be slightly alkaline ; 

 the growth is slow. 



Colonies on Gelatine Plates. Since the temperature must be 

 somewhat elevated, the gelatine media need to be thicker than 

 usual (15 per cent, gelatine), in order to keep it solid, and a 

 temperature of 24 C. used. Little round white colonies, some- 

 what granular in the centre, growing very slowly. 



Stab Cultures. Along the needle-track small separate white 

 granules, one above the other, like a string of beads. 



Stroke Culture. On agar, transparent, almost invisible little 

 drops resembling dew moisture. 



Bouillon. They grow better here than in the other media, 

 remaining alive a longer period of time. 



St am ing. Takes Gram's method and the other aniline stains 



