82 BACTERIOLOGY. 



For the filtration of such substances as gelatin and 

 agar-agar it is of much importance to have a properly 

 folded filter. To fold a filter correctly, proceed as fol- 

 lows : A circular piece of filter paper is folded exactly 

 through its centre, forming the fold 1,1' (Fig. 18) ; the 

 end 1 is then folded over to 1', forming the fold 5 ; 1 

 and V 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 

 produced ; 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 produced is to be subdivided by a seam or 

 fold through its centre, as indicated by the dotted lines 

 in Fig. 13, but with the creases on the side opposite to 



FIG. 14. 



that occupied, by the creases 1, 2, 3, 4, etc., first made. 

 As each of these folds is made the paper is gradually 

 folded into a wedge-shaped bundle (Fig. 14 a), which 

 when opened, assumes the form of a properly folded 

 filter seen in 6, Fig. 14. Before placing it upon the 

 funnel it is well to go over each crease again and see 

 that it is as tightly folded as possible, without tearing 



