PATHOGENIC BACTERIA. 129 



Form. A very delicate, slender rod, somewhat longer than 

 the bacillus of mouse septicaemia, which is the smallest bacillus. 



When the spores form, a small swelling occurs at the end 

 where the spore lies, giving it a drum-stick shape. 



FIG. 72. 



Bacillus of Tetanus with spores. 



Properties. Not very motile, though distinctly so ; liquefies 

 gelatine slowly. The cultures give rise to a foul-smelling gas. 



Growth. Develops very slowly, best at brood-heat (36 to 38 

 C.), and only when all oxygen is excluded, an obligatory ancero- 

 bin. In an atmosphere of carbon dioxide gas it cannot grow, 

 but in hydrogen it flourishes. 



Colonies on gelatine plates in an atmosphere of hydrogen. 

 Small colonies. After four days a thick centre and radiating 

 wreath-like periphery, like the colonies of bacillus subtilis. 



High Stab-Culture. (The gelatine having 2 per cent, glucose 

 added and filling the tube.) Along the lower portion of the needle- 

 track, a thorny-like growth, little needle-like points shooting 

 out from a straight line. The whole tube becomes clouded as 



