io6 Elements of Water Bacteriology. 



gas ratio is a function of the total quantity of gas seems 

 us justified. The determination of the gas ratio may 

 therefore be omitted, and any tests which show from 10 to 

 80 per cent gas in dextrose broth in forty-eight hours may 

 be considered positive. 



For recording the results of the various tests applied 

 in sanitary water examination, the appended blank form 

 has been in use at the Massachusetts Institute of Tech- 

 nology. On the upper part of the sheet are noted the 

 results of the gelatin count and the litmus-agar count at 

 37 degrees. In the second column the number of acid- 

 formers is placed in brackets after the total numbers. 

 The lower part is used for the B. coli isolation. 



MASSACHUSETTS INSTITUTE OF TECHNOLOGY. 

 Bacteriological Examination of Water. 



Sample No. Date of collection 



Examined by Hour of collection 



Place of collection Remarks 



Number of Bacteria. 



Gelatin-plate cultures. No. colonies Agar-plate cultures at 37. 

 48 hours. per c.c. No. colonies per c.c. 



24 hours 



Average Average 



Remarks Remarks 



B. Coli Isolation. 



Preliminary fermentation tube 

 Litmus-lactose-agar plates 

 Agar streak culture 

 Fermentation tube 

 Nitrate test 

 Milk test 

 Indol reaction 

 Gelatin-stab culture 

 Remarks 



