4 i8 



BACTERIOLOGICAL ANALYSES 



cm. long, reaching to near the bottom of the bottle, 

 each tube projecting about 2.5 cm. above the rubber 

 stopper. Plug the open ends of the tubes with cotton 

 wool. Secure the stopper in place with thin copper wire. 

 Sterilise the fitted bottle in the autoclave. Remove 

 the cotton wool plugs and connect the projecting 

 tubes by a piece of loosely fitting stout rubber pressure 

 tubing about 5 cm. long, previously 

 sterilised by boiling. 



Take a piece of stout rubber cord 

 about 33 cm. long, and of 10 mm. diam- 

 eter (such as is used for door springs) 

 thread a steel split ring upon it and 

 secure the free ends tightly to the neck 

 of the bottle by cord or catgut. 



Attach the cord used for lowering the 

 bottle into the water to the split ring 

 on the rubber suspender. The best ma- 

 terial for this purpose is cotton insulated 

 electric wire knotted at every metre. 



Connect the split ring also with the 

 short piece of rubber tubing uniting 

 the two glass tubes by a piece of catgut 

 (or thin copper wire) of such length 

 that when the bottle is suspended there 

 Thresh's ' deep is no pull upon the rubber tube, but 

 bo a ttie. Sampling which > however, will be easily jerked off 

 when a sharp pull is given to the sus- 

 pending cord. 



Now wind heavy lead tubing about i cm. diameter 

 around the upper part of the bottle, starting at the 

 neck just above the shoulder. This ensures the sinking 

 of the bottle in the vertical position (Fig. 204). 



The apparatus being arranged is lowered to the 

 required depth, a sharp jerk is then given to the sus- 

 pending cord, which detaches the rubber tube and so 

 opens the two glass tubes. Water enters through the 



