450 



Dr. T. Carnelley and Mr. T. Wilson. 



of glass tube about 8 inches long and | inch* internal diameter. It 

 extends about two-thirds of the way down the flask, and is closed at 

 the outer end by a glass stopper B, fitted on with a piece of india-rubber 

 tubing. Into the other hole of the stopper is fitted the " exit tube " 

 CC. This is simply a piece of ordinary glass tubing (about J inch 



Fig. i. 



diameter) bent round at the lower end so that it opens in the neck 

 of the flask just under the india-rubber stopper. It is open at both 

 ends, but contains two cotton-wool plugs to prevent any micro- 

 organisms passing back into the flask from the outside air. 



10 c.c. of Koch's gelatine-peptone are introduced into the flask and 

 the stopper tied on with copper wire. The flask is then sterilised by 

 heating in steam at 100° C. for an hour and allowed to cool, whereby 



* The entrance tube must have at least this width, for if it be too narrow, mois- 

 ture from the jelly forms during sterilisation on the inside of the tube, and on 

 cooling runs down and collects as a drop on the end, so that the air, on entering the 

 flask, has to pass i hrough this drop of water, which thus retains some of the micro- 

 organisms, and so vitiates the results. This, however, is entirely obviated by using 

 a tube of the prescribed width. 



