310 WATER HYGIENE 
Methyl red — 
Voges-Proskauer-+ 
Gelatin — 
Adonite-+ 
Indol, usually + 
Saccharose-+ 
Methyl red— 
Voges-Proskauer-++ 
Gelatin — 
Adonite — 
Indol, usually — 
Saccharose-+ 
Methyl red — 
Voges-Proskauer-+ 
Gelatin-+ 
Adonite+ 
Indol, usually — 
Saccharose-+- 
B. aerogenes of fecal origin 
B. aerogenes, probably not of fecal origin 
B. cloace, or may not be of fecal origin 
The Treasury Department Standard for the Examination of Water 
on Interstate Common Carriers. The following method for the exam- 
ination of water on Interstate common carriers has been formulated 
by a committee of prominent sanitarians. The permissible limits of 
bacteriological impurity are stated as follows: 
1, The total number of bacteria developing on standard agar plates, in- 
cubated twenty-four hours at 37° C., shall not exceed 100 per cubic centimeter; 
provided, that the estimate shall be made from not less than two plates, showing 
such numbers and distribution of colonies as to indicate that the estimate is 
reliable and accurate. 
2. Not more than one out of five 10 c.c. portions of any sample examined 
shall show the presence of organisms of the Bacillus cols group when tested as 
follows: 
(a) Five 10 ¢.c. portions of each sample tested shall be planted, each in a 
fermentation tube containing not less than 30 ¢.c. of lactose peptone broth. 
These shall be incubated forty-eight hours at 37° C. and observed to note gas 
formation. 
(b) From each tube showing gas, occupying more than 5 per cent of the 
closed arm of fermentation tube, plates shall be made after forty-eight hours’ 
incubation, upon lactose litmus agar or Endo’s medium. 
(c) When plate colonies resembling B. coli develop upon either of these plate 
media within twenty-four hours, a well-isolated characteristic colony shall be 
