36 ELEMENTS OF WATER BACTERIOLOGY 



from several inches down, as the surface itself is likely 

 to have dust particles floating upon it. The method 

 most frequently recommended is to plunge the bottle 

 mouth downward to a depth of a foot or so, then 

 invert and allow the bottle to fill. 



Whenever any current exists, the mouth of the bottle 

 should be directed against it in order to carry away any 

 bacteria from the fingers. If there is no current, a 

 similar effect can be produced by turning the bottle 

 under water and giving it a quick forward motion. In 

 rapidly flowing streams it is only necessary to hold 

 the bottle at the surface with the mouth pointed 

 up-stream. 



For taking samples of water at greater depths, a 

 number of devices have been employed, all of which 

 are fairly satisfactory. The essentials are, first, a weight 

 to carry the bottle down to the desired depth, and, 

 second, some method of removing the stopper when 

 that depth is reached. The student will find one good 

 form of apparatus described in Abbott's " Principles 

 of Bacteriology" (Abbott, 1899); an admirable one 

 was devised by Hill and Ellms (Hill and Ellms, 1898); 

 and Thresh (1904) figures an ingenious device for the 

 same purpose. Miquel and Cambier (Miquel and 

 Cambier, 1902) and other authors recommend the use 

 of a sealed glass bulb with a capillary tube which can 

 be broken off at the desired moment. Drew (1912) 

 has devised an interesting sampling apparatus for use 

 at great depths in the sea. 



Changes in Bacterial Numbers after Sampling. As 

 soon as a sample of water is collected its conditions 



