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BACTERIOLOGY 



When the gelatin is completely melted it may be filtered 

 through a folded paper filter supported on an ordinary 

 funnel; if solution is complete, this should be very quickly 

 accomplished. 



To Fold a Filter. For the filtration of such substances 

 as gelatin and agar-agar it is of mportance to have a 

 properly folded filter. Inability to fold a filter properly is 

 so common with beginners that a detailed description of 

 the steps may not be out of place. To fold a filter cor- 

 rectly, proceed as follows: A circular piece of filter paper 

 is folded exactly through its center, forming the fold 1, 1' 



(Fig. 16); the end 1 is then folded over to 1', forming the 

 fold 5; 1 and 1' are each then brought to 5, thus forming 

 the folds 3 and 7; 1 is then carried to the point 7, and the 

 fold 4 is formed, and by carrying V to 3 the fold 6 is pro- 

 duced; and by bringing 1 to 3 and 1' to 7 the folds 2 and 8 

 result. 



Thus far the ridges of all folds are on the side of the paper 

 next to the table on which we are folding. The paper is 

 now taken up and each space between the seams just pro- 

 duced is to be subdivided by a crease or fold through its 

 center, as indicated by the dotted lines in Fig. 16, but with 



