CHAPTER XVI. 



SUMMARY OP THE PROCEDURE RECOMMENDED 



FOR THE BACTERIOLOGICAL EXAMINATION 



OP WATER AND PREPARATION OP 



NUTRIENT MEDIA. 



A. Quantitative Analysis : 



Shake a portion of the sample gently, but thoroughly, so as 

 to break down clumps of bacteria. Ascertain roughly the 

 probable number of micro-organisms present by means of a 

 cover-glass preparation, and if necessary dilute the specimen 

 with sterile tap-water. Make three gelatine plates with an 

 amount of the water which will not produce more than 300 

 colonies in each plate. As a rule, T V c.e. ? J c.c., and | c.c. will 

 be found suitable amounts for the plates. Incubate the plates 

 at 22 C. for as long as possible. Count the colonies day by 

 day, and record the average number which develop per c.c. 



B. Qualitative Analysis : 



(1) If the specimen does not contain many bacteria, pump 

 one or two litres through a Berkefeld or Pasteur-Chamberland 

 candle, and diffuse the deposit in 5 to 10 c.c. of sterile water. 

 Treat this as follows : 



(a) Add 1 c.c. of the concentrated water to 15 c.c. of sterile 

 whole milk, heat to 80 C. for ten minutes, cool, and then 

 incubate at 37' C. in a Buchner tube. Note if any changes 

 characteristic of B. enteritidis sporogenes are produced within 

 twenty-four to thirty-six hours. 



(b) Plate in carbolic acid gelatine (0*05 per cent, carbolic- 

 acid) from O'l to 1 c.c. of the concentrated water. 



(c) Add from O'l to 1 c.c. of the concentrated water to broth 

 tubes containing 0*05 per cent, carbolic acid, and incubate the 

 tubes at 37 C. ; or add the same amounts of the concentrated 



