LIQUID MEDIA. 97 



A small piece of putty or modelling wax is rolled 

 into a cord about two inches long and inch thick. 

 By uniting the ends a ring is formed, which is placed 

 on the middle of a clean glass slide (Fig. 31). A 

 drop of water is placed in the centre of the ring, 

 and the cell roofed in by applying the cover-glass. 



A somewhat similar cell in form, which has the 

 advantage of permitting of thorough cleansing, may 



FIG. 31. METHOD OF FORMING A SIMPLE MOIST-CHAMBER. 



be constructed by cementing a glass ring with flat 

 surfaces to an ordinary slide. Vaseline is applied 

 with a cameF s-hair brush to the upper surface of 

 the ring, and one or two drops of water placed with 

 a pipette at the bottom of the cell. The cover- 

 glass, with the preparation, is then inverted over 

 the cell and gently pressed down upon the glass 

 ring. The vaseline renders the cell air-tight, and, 

 to a certain extent, fixes the cover-glass to the ring. 

 Warm Stages. To apply warmth while a pre- 

 paration is under continuous observation we must 



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