154 BACTERIOLOGICAL EXAMINATION OF WATER. 



X it rate-broth. No reduction of nitrates to nitrites in twenty- 

 four hours at 37 C. 



Microscopical Characters. Medium-sized bacillus with rounded 

 ends, solitary, in pairs, and in chains. Very motile, possesses 

 numerous flagella, and forms spores. Grows with great rapidity 

 at 37 C. 



Remarks. This micro-organism is probably identical with 

 Bacillus mesenterictis vulgatus. 



Bacillus Subtilis (Sewage variety A.). 



Isolated from crude sewage and effluents from coke-beds. 



Gelatine-plate Cultures. In two days at 20 C. it forms circular 

 greyish- white areas of liquefaction ; masses of bacteria in the lique- 

 fied gelatine may give the colony a mottled appearance. Under a 

 low power the bacilli at the margin of the colony are seen to bore 

 into the gelatine, side by side, in a highly characteristic manner. 



Gelatine-stab. In two days at 20 C. the gelatine is liquefied 

 down to the foot of the stab. A scum forms on the surface, 

 but no distinct skin is formed. 



Agar-streak. In two days at 37 C. there is an abundant 

 creamy-white layer covering nearly the whole surface, which 

 shows numerous minute circular areas where the growth, instead 

 of being opaque, is semi-transparent. 



Gelatine-shake. There is no gas formation. 



Broth Cultures. Diffuse cloudiness in twenty-four hours at 

 37 C. A scum forms on the surface, which readily falls to the 

 foot of the tube on shaking. 



Indol. There is no formation of indol. 



Litmus-milk. In two days at 37 C. there is complete dis- 

 coloration and a clot has formed ; no redness is visible. In five 

 days a white clot occupies about one-third of the bulk of the 

 medium, which appears to be slowly peptonised. The liquid 

 surrounding the clot is pale yellow in colour, semi-transparent, 

 and without pink coloration. 



Potato Cultures. In two days at 37 C. a dirty-white layer 

 is formed with a yellowish tint. 



Microscopical Appearances. Large, long bacillus with rounded 

 ends, frequently in long chains. It forms spores and has 

 a waddling, sluggish movement. It grows well at 37 C. 



