BACTERIOLOGICAL TECHNIC 23 



c) Fold this to make i cover 2 and 3 cover 4 (result 

 Fig. 13^). It consists of four layers and forms a square. 



d) Fold the upper part, consisting of two layers, 

 from i to 2 (Fig. 13^). The shaded triangle, 2-3-4, 

 now has six layers; the other, 1-3-4, two layers. 



a, 



FIG. 13 



Method of Folding Paper Filter 

 (For reference letters see text) 



e) Fold the upper double layer so as to make 2 

 cover a point in the diagonal at 5, taking care to make 

 a sharp point at 4 (result Fig. 130). The shaded part 

 is now eight layers deep. 



/) Turn the folded part face down and repeat 



