64 BACTERIOLOGICAL ANALYSIS. 



of broth, to make gelatine. To it he adds 1% of po- 

 tassium iodide). Pour plates in the usual manner. 

 This medium has the same effect on bacterial growth as 

 the carbolic gelatine. 



4. Add .1 cc. of the water to 6 or more peptone 

 tubes, and incubate for 24 hours at 37°C. Strips of fil- 

 ter paper, moistened with a solution of acetate of lead 

 may be fixed to the stoppers. Putrefactive bacteria de- 

 velop sulphuretted hydrogen during growth, and if this 

 is formed, the lead paper, is blackened. The indol test 

 may also be applied, with and without the addition of 

 nitrites. Plates may also be made from the surface of 

 the fluid, and the bacteria present, separated and identi- 

 fied. 



Peptone solution is used extensively when examin- 

 ing for the Spirillum of Asiatic Cholera. The method 

 used is either to use the " concentrate,' 7 as described in 

 (5), or to add to 50 cc. flasks of peptone, from 10 to 25 

 cc. of the water. 



After 16 to 18 hours, the surface layers of the fluid 

 are examined microscopically for vibrios: If these are 

 present apply indol tests, and make subcultures on gela- 

 tine and agar plates, to separate and identify the 

 species. 



5. Filter through a Berkfeld or Chamberland candle, 

 into a sterile flask, 500 cc. of the water to be examined. 

 Place about 20 cc. of the filtered water, (which is 

 " sterile "), into a sterile beaker, and with a sterile brush 

 scrape the filter candle surface into the water. This 

 " concentrates " the bacteria present, in the water. The 



