ROUX TUBES 



85 



manner at the point of constriction, and 

 strengthen the points of closure by the applica- 

 tion of a little Golatz wax while the glass is still 

 hot. Allow solidification of the medium to take 

 place, and place in the incubator at 22° C. 



The colonies quickly develop, scattered in 

 the gelatine, the first indication of growth being 

 the decoloration of the medium due to the 

 reduction of any remaining trace of oxygen by 

 the organisms introduced. 



When it is desired to culture, reculture, or 

 to examine any particular colony, it is only 

 necessary to make a file mark at the point de- 

 sired, pass the tube lightly two or three times 

 through the flame in ordar to sterilise the 

 exterior and slightly to liquefy the gelatine 

 adhering to the walls of the tube, break ofif 

 first one end of the tube and then the tube 

 itself at the file mark, and, by blowing gently 

 through the tube orifice, expel the contents into 

 a sterile Petri dish. Any desired colony can 

 then without difficulty be picked out on the 

 point of a platinum needle and either examined 

 under the microscope, or recultured as desired. 



2. Roux tube for cultures in milk, bouillon, 

 OP other liquid media — 



For cultures in liquid media under strict 

 anaerobic conditions, the method of Roux will 

 be found most efficacious. The tube consists 

 of a piece of f inch glass tubing, drawn out at 

 an extremity to a gradually reducing pipette of 

 from 8 to 9 inches in length, leaving above it 

 some 4 or 5 inches of the full-sized tube, to the 

 other extremity of which is fused on a length 

 of smaller tubing of about 7 inches. In this 

 latter two constrictions are made, a cotton-wool 

 plug being placed in position between the two. 

 The tubes when made are sterilised at 1 50° C. 



A tube of sterile milk or bouillon is inocu- 

 lated in the ordinary manner. After breaking 

 off the pipette point, sterilising the exterior 



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