BACTERIOLOGY OF WATER AND MILK 111 



(Agar esculin bile salt at 38 C. Two with 1 cc. each- 

 one with 10 cc. in large dish.) 

 Fermentation tubes. 



"Dextrose-peptone. Ten tubes with 1 cc. each; five tubes 

 with 0.1 cc. each. A 2% dextrose solution in water, 3% white 

 peptone ("Witte). and 0.5% potassium chloride with a reaction 

 1.5 and 1.0 per cent. 



"Lactose-peptone. Ten tubes with 1 cc. each; five tubes 

 with 0.1 cc. each. Same as dextrose peptone by substituting 

 lactose for dextrose. 



"Dextrose-peptone to which five drops of 5 per cent phenol 

 are added. 1 Ten with 1 cc. each, five with 2 cc. each. Incu- 

 bate at 42 C. 



"The colonies on agar plates incubated at 37 C. to 38 C. 

 should be counted at the end of twenty-four hours, and again 

 after forty- eight hours. 



"The colonies on gelatin and agar plates at 20C. should 

 be counted after forty-eight hours' standing and if possible 

 again after seventy-two hours. When the number of colonies, 

 developing upon a plate are few it is the best plan to allow 7 the 

 plates to remain as long as possible in the incubator before 

 making the final counts in order that slow growing species may 

 become apparent and that all the species present may develop 

 sufficiently to exhibit their characteristic appearances." 



The methods of making culture media and cultures in 

 water analyses recommended by the Committee on Water 

 Analysis of the Laboratory Section, American Public Health 

 Association, 1905 4 are considered as standard. They are gen- 

 erally followed in work of this kind. 



The interpretation of the bacterial findings. The spe- 

 cies common to water and soil are not known to be possessed of 

 any direct sanitary significance. The fecal bacteria are rep- 

 resented largely by B. coli, B. aerogenes and streptococci. The 

 presence of these species shows that the conditions are favor- 



1 Method of Vincent. Mace. Traitre de Bacteriologie, edition,, 

 p. 711. 



4 Supplement of the Journal of Infectious Diseases, 1905, p. 1.. 



