BACTERIOLOGY OF SEWAGE 203 



The following scheme (adapted by Moor and Hewlett, 

 after Houston) is applicable to sewage and effluents. A 

 fair average sample of the sewage or effluent must be 

 obtained by mixing portions obtained at intervals. The 

 mixture should be strained through muslin. 



Tests. 



Procedure. 



1. Total number Gelatin and agar 

 of bacteria i cultivations 



'2. Num bor of 'Gelatin plate cultures 



spores of ae- with material pre- 



robes viously heated to 



30 C. for ten minutes 



plate 0-001, 0-0001, 

 0-00001 



1-0, 0-1, -0-01 



3. Number of Agar plate cultures with 

 spores of an- material previously 

 aerobes heated to 80 C. for ten 



minutes and incubated 

 anaerobically 



4. Number of Surface gelatin plates 



organisms 

 liquefying 

 gelatin 



5. Spores of B. Milk cultures (see p. 



Wdchii 



6. Number of B. Surface Conradi-Drigal- 



coli ski plates, or bile salt 



broth 



7. N u m b e r of Surface plates of Conradi 



streptococci Drigalski medium 



Amount of Sewage 

 in c.c. 



1-0, 0-1, 0-01 



0-001, 0-000 1, 

 0-00001 



87) 0-1, 0-01, 0-001 



0-001, 0-0001, 

 0-00001 



0-01, 0-001, 0-0001 



In addition, effluents should be submitted to the two 

 following tests: 



1. Incubate some in beakers at 22 C. and 37 C. for 

 some days. A good effluent should yield little or no 

 unpleasant odour (an unpleasant odour indicates the 



