206 AIDS TO BACTERIOLGOY 



same length as, but somewhat narrower than, the anthrax 

 bacillus. It has rounded ends, grows into long threads, 

 and is very motile, having long flagella; forms ovoid 

 spores about I '2 /LI long by 0*6 // broad, which germinate 

 at right angles to the long diameter, and are very resistant 

 to heat, surviving dry heat of 120 C. for one hour (see 

 p. 9). The bacillus is strictly aerobic and Gram-positive. 

 The colonies on gelatin plates become visible in about 

 two days, as small white dots in the depth, whereas on 

 the surface they show small greyish liquefied circles. 

 In a gelatin stab a liquefied funnel-shaped depression 

 forms, the lower part throwing out lateral feathery 

 extensions. The whole of the gelatin is soon liquefied, 

 and a tough pellicle forms on the surface, and a quantity 

 of flocculent matter collects at the bottom of the tube. 

 A white, opaque, moist expansion is formed on agar, 

 which afterwards becomes dry and furrowed; a uniform 

 turbidity with pellicle develops in broth, and a moist 

 cream-like expansion, dull and never shining, forms over 

 the whole surface of potato. 



B. ramosus (wurzel bacillus] strongly reduces nitrates 

 to nitrites. The bacillus is Gram -positive, about 7 ju 

 long and 1-7 p broad, with rounded ends. It occurs in 

 long threads, and has resistant spores. On gelatin plates 

 cloudy centres, with root-like branches extending in every 

 direction, are seen; the gelatin is slowly liquefied. In 

 gelatin stabs a slight depression is seen after the second 

 day, whilst the needle track in the depth has a greyish 

 woolly appearance. The whole contents of the tube then 

 becomes liquid, a tough pellicle forming on the surface. 

 It grows on carbolated media. It grows rapidly over 

 the whole surface of agar; in the depth is seen the charac- 

 teristic woolly appearance. A white dry expansion is 

 formed on potato. 



B. mesentericus fuscus and B. mesentericus vulgatus 

 (' potato bacillus ') are found on vegetables and in water. 

 They are short, motile, sporulating, Gram-positive organ- 

 isms, which liquefy gelatin. Fuscus forms a yellowish- 

 brown growth on agar, while vulgatus gives a dirty white 

 growth. Bed (ruber) and black (niger) varieties are also 

 known. 



B. tholoeideum. An intestinal organism invariably 

 found in sewage. It produces a septicaemia in mice and 



