43 6 



BACTERIOLOGICAL ANALYSES 



bottle with sulphuric acid between the filter flask and 

 the force-pump (in the position occupied in the diagram 

 by the central vertical line) , and placing another screw 

 clamp on the rubber tubing connecting the lateral arm 

 of the filter flask with the wash-bottle. 



2. Filter the entire 2000 c.c. of water 

 through the filter candle. 



3. When the filtration is completed, 

 screw up the clamps and so occlude the 

 two pieces of pressure tubing. 



4. Reverse the position of the glass tubes 

 in the Wulff's bottle so that the one 

 nearest the air pump now dips into the 

 sulphuric acid. 



5. Slowly open the metal clamps and 

 allow air to gradually pass through the 

 acid, and enter filter flask, and so restore 

 the pressure. 



6. Unship the apparatus, remove the 

 cork from the mouth of the candle. 



7. Pipette 10 c.c. of sterile broth into 

 the interior of the candle, and by means 

 of the sterile test-tube brush (Fig. 210) 



Sterile test-tube emulsify the slimy residue which lines the 

 brush - candle, with the broth. 



Practically all the bacteria contained in the original 

 2000 c.c. of water are now suspended in 10 c.c. of 

 broth, so that i c.c. of the suspension is equivalent, 

 so far as the contained organisms are concerned, to 

 200 c.c. of the original water. (Some bacteria will of 

 course be left behind on the walls of the filter and in 

 its pores.) 



Up to this point the method is identical, irrespective 

 of the particular organism whose presence it is desired 

 to demonstrate ; but from this point onward the methods 

 must be specially adapted to the isolation of definite 

 groups of organisms or of individual bacteria. 



