438 MICRO-ORGANISMS IN WATER 



BACILLUS DELICATULUS 



LIQUEFIES GELATINE 



Authority. — Jordan, A Beport on certain Species of Bacteria 

 Sewage, State Board of Health, Massachusetts, 1890, p. 837. 



"Wliere Found. — In effluent from Lawrence sewage. 



Microscopic Appearance.— Medium-sized, plump bacilli, 2^ long and 1 ju. 

 broad, often joined in pairs and in short strings. Very motile. No spore 

 formation observed. 



Cultures.— 



Gelatine Plates.— When young the colonies are whitish, homogeneous, 

 with a regular, radiating edge. In two days, at the temperature of the roora^ 

 the gelatine becomes liquefied ; later the centre becomes darker than the sur- 

 rounding zone. 



Gelatine Tubes.— In two days the gelatine is liquefied the length of the 

 needle's path, and in about seven days the whole contents of the tube are fluid 

 and cloudy. A thick, whitish skin forms on the surface, and a heavy, floccu- 

 lent, brownish precipitate at the bottom. Grows nearly as well in slightly acid 

 gelatine as in alkaline. 



Agae-agah. — Forms at first a crinkled greyish growth, which when older 

 becomes porcelain-white and glistening. Grows well both on the surface and 

 below. 



Potatoes. --A grey, spreading and fiat growth. 



MiLK.^The milk is coagulated, and gives a strong acid reaction. 



Bkoth.— The liquid quickly becomes turbid, and a. white precipitate and 

 scum are produced. 



Bemarks. — Reduces nitrate to nitrite very rapidly and completely (see J5. cloacae). 

 It is very sensitive to low temperatures. At about 15° C. it refuses to grow at all. 

 After several weeks no living bacilli were obtained from tube cultures. 



BACILLUS EUBESCENS 



Authority. — Jordan, A Report on certain Species of Bacteria ohserved in 

 Sewage, State Board of Health, Massachusetts, 1890, ' Sewage and Water,* 

 p. 835. 



"Where Found. — In the Lawrence sewage. 



Microscopic Appearance. — Large, long bacilli, about 4 fx long and^ m broad, 

 with well rounded ends. Often occurs in pairs and short strings, filany of the 

 individual bacilli are slightly curved. No spore formation observed. Slow 

 and sluggish movement. 



Cultures. — 



Gelatine Plates.— Grows slowly. The depth colonies are usually round, 

 sometimes oval. They form pin-head, porcelain-white, drop-like projections on 

 the surface. Later they become slightly brownish. 



Gelatine Tubes.— Grows slowly and chiefly on the surface, forming a 

 porcelain- white, nail-head projection. Grows only slightly in the depth. No 

 liquefaction ensue^. 



Agak-agah. — Grows rapidly, producing a white lustrous and smooth expan- 

 sion. Later this becomes crinkly, and the w4iole surface is much wrinkled. 

 In three weeks old cultures a slight pinkish tinge can be seen. 



Potatoes. — Produces a luxuriant, light-brown, raised growth, which later 

 becomes pink and flesh-pink in colour. The potato itself is not coloured. 



Milk. — The milk is not coagulated, and in long-standing cultures a slight 

 pinkish tinge is observed at the surface. 



Broth. — Forms a heavy white precipitate, and the liquid is rendered turbid. 

 A thick, tenacious skin forms much later on the surface, and the main body of 

 the liquid is then clear. 



Remarks. — No change in the nitrates after fifty days. (See under B. cloacae, 

 p. 433.) 



