QUALITATIVE BACTERIOLOGICAL ANALYSIS. 145 



SEWAGE BACTERIA, ISOLATED BY HOUSTON, FROM LONDON 

 CRUDE SEWAGE AND THE EFFLUENTS FROM COKE-BEDS. 



The latest contribution to the study of sewage flora has been 

 made by Houston, who, during his studies of the bacterial 

 treatment of sewage, isolated a number of micro-organisms 

 which appeared to be new species and peculiar to sewage. The 

 following descriptions are taken from the second report on the 

 bacterial treatment of sewage, presented to the London County 

 Council. 



Sewage Proteus. 



Source. Very abundant in London crude sewage ; frequently 

 as many as 100,000 per c.c. of crude sewage. 



Gelatine-plate Cultures. In less than twenty-four hours at 

 20 C. the surface colonies appear as delicate granular films 

 of an irregular shape. In two days the colonies look like 

 " punched out " circles, containing liquefied gelatine and greyish- 

 white bacterial deposit. The masses of bacteria lying in the 

 liquefied gelatine give the colonies a mottled appearance. 

 Under a low power the individual bacilli can be made out, and 

 their active movement watched. The colonies are usually 

 exactly circular in shape, with well -defined borders, and no 

 " swarming islands " appear to be given off as in the Proteus 

 vulgaris. By the third or fourth day the plate is completely 

 liquefied. 



Gelatine-stab Culture. The growth is very characteristic, in 

 twenty-four hours at 20 C. liquefaction has occurred all the 

 way down the path of the needle, and minute bubbles of gas 

 may be seen rising to the surface through the turbid liquefied 

 gelatine. In forty-eight hours the liquefaction is more pro- 

 nounced, and numerous bubbles may be seen at the surface, and 

 also bubbles in the solid gelatine. The bacteria collect at the 

 foot of the liquefied portion, as a greyish-white deposit. In 

 four or five days the whole of the gelatine is converted into a 

 greyish- white liquid. 



Gelatine-shake Cultures. In twenty -four hours at 20 C. 

 numerous gas bubbles are formed, and the gelatine is liquefied 

 near the surface. 



