CHAPTER XII. 



QUALITATIVE ANALYSIS continued. 



" SEWAGE-BACTERIA " DESCRIBED BY E. O. JORDAX. 



IN 1890 Jordan made a special study of bacteria occurring in 

 sewage. He believed that sewage was probably inhabited by 

 species peculiarly adapted to the conditions of life, and thought 

 there was good reason for speaking of "sewage bacteria," i.e., those 

 bacteria normally found in sewage, and composing its special 

 flora. The following micro-organisms were found in the Law- 

 rence sewage, and appeared to be peculiar to this medium. 

 The descriptions are taken from Jordan's paper in the Report 

 of the Massachusetts State Board of Health for 1890. 



Bacillus Cloacae. 



This bacillus appeared to be one of the commonest bacteria 

 in sewage. 



Plate-cultures. In twenty-four to forty-eight hours a round, 

 yellowish colony becomes visible in the gelatine. On coming to 

 the surface this forms a slight bluish expansion, with irregularly 

 notched edges, and almost immediately begins to liquefy the 

 gelatine. Under a low power of the microscope, the colony is 

 seen to have a dark centre, an outer translucent zone and a 

 darker edge ; the interior is finely granular. The whole plate 

 is soon liquefied (in from three to four days). 



Gelatine-tubes. A rapid growth, liquefying the gelatine. A 

 good growth along the inoculation line. An iridescent scum 

 forms on the surface, and there is a heavy, whitish, flocculent 

 precipitate. Grows as well in slightly acid gelatine as in the 

 slightly alkaline medium. 



Agar-tubes. A moist, slimy, porcelain-white surface growth. 

 Excellent growth along the inoculation line. 



