QUALITATIVE BACTERIOLOGICAL ANALYSIS. 49 



B. Aquatilis Sulcatus. 



Colonies on Gelatine Plates. After forty-eight hours incuba- 

 tion at 22 C. the colonies appear on the surface as bluish-white 

 films with an irregular margin ; the centre is thicker than the 

 periphery. Under a low power numerous fine lines are seen 

 passing from the centre to the periphery, producing an appear- 

 ance closely resembling the ridges and valleys on the colonies of 

 B. typhosus. Later, the centre of the colony acquires a yellow 

 colour. The gelatine is not liquefied. 



Gelatine-stab. The surface growth exactly resembles a colony ; 

 there is a scanty growth along the stab. 



Agar-slope. A white smooth growth ; later, becomes yellow 

 in colour. 



Glucose-gelatine (shake). No gas formation. 



Peptone-water. No indol reaction obtained. 



Milk. Unchanged. 



Potato. A thin yellow film appears. 



Nitrate-broth. No reduction of nitrates. 



Broth. Diffuse growth, no pellicle appears on the surface. 



Microscopical Appearance. A small motile bacillus with 

 rounded ends, closely resembling B. typhosus. It does not form 

 spores and is decolorised by Gram. It will grow at 5 C., but 

 develops very feebly at 37 C. 



The above description corresponds with B. Aquatilis sulcatus V. 

 Four other varieties were described by Weichselbaum. No. I. 

 differs from the type in that at 37 C. it produces a thick 

 white expansion on agar, and on potato it produces at first only 

 a moist appearance, which later becomes cream-coloured. No. II. 

 shows colonies which are thicker than the above, and the system 

 of lines is hardly visible ; the growth on potato has a yellow-blue 

 colour which later becomes yellowish-grey or yellowish-brown, 

 and is often very luxuriant. No. III. produces colonies re- 

 sembling the type ; but the growth on potato has a bright yellow- 

 colour. Bacillus No. V. shows typical colonies, but does not 

 produce any growth on potato. 



The B. sulcatus is an important organism to recognise, owing 

 to its strong resemblance to the typhoid bacillus ; it is, however, 

 easily differentiated by the colonies acquiring a yellow colour 



