LESSON III 



lination of Water I. Quantitative Examination by Plate Culture 

 Method and Roll Tubes Effect of Sunlight on Water. 



I. Quantitative Examination of Water 



COLLECT the water to be tested in a sterilised flask. 



(a) If tap water, allow it to run for a minute or two 

 before collecting it. 



(&) If stagnant water or river water, collect it from 

 varying depths with special pipettes or bottles, and empty 

 the latter into sterilised flasks. 



A. TAP WATER. 



(a) Plate culture method. 



(1) Collect 100 cc. of the water to be examined in a 

 sterilised flask, and shake the latter. 



(2) With a sterile graduated pipette, connected with a 

 short india-rubber tube, suck up *25 cc. of this water, and 

 add it severally to each of three liquefied gelatine tubes. 



To sterilise the pipette, it should be plugged with 

 cotton-wool at its broad end (a), and placed in a 

 test-tube, the mouth of which is also plugged with 



