60 MICRO-ORGANISMS IX WATER 



CHAPTER III 



THE EXAMINATION OF WATER FOR MICRO-ORGANISMS 



Collection of samples. Samples of water for bac- 

 teriological examination may be collected in flasks 

 plugged with cotton-wool, 1 in glass bottles closed with 

 tightly fitting glass stoppers, or in sealed flasks from 

 which the air has been exhausted, and the necks of 

 which have been drawn out to a fine point. This fine 

 point is broken off under water, and after the latter 

 has rushed in to fill the vacuum, the flask is sealed 

 up again on the spot in the flame of a spirit lamp. 



All these vessels must of course be carefully 

 sterilised before use in the hot-air oven. For general 

 purposes it will be found most convenient to use small 

 wide-mouthed glass-stoppered bottles of about 60-100 

 c.c. capacity. These, after careful washing and rinsing 

 with distilled water, are dried in the oven, each stopper 

 being laid across the mouth and not fitted into the 

 neck of the bottle to which it belongs. When quite 

 dry the stoppers are tightly inserted, and each bottle 

 is shut up in a separate small tin canister ; these 

 canisters with their enclosed bottles are then heated for 

 two to three hours at 150 C. in the oven. The bottles 

 are transported in their canisters to the place where 

 the water is to be collected, and not until the moment 



1 In the case of samples which have to be transported any consider- 

 able distance before reaching the laborator3 T cotton-wool stoppers are not 

 advisable. 



