154 



The Preparation of Microscope Slides 



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Fig. 117. Warming the flooded ribbons to flatten them. 



under the sections, either causing them to fall off or at least making it 

 very difficult to observe them properly when mounted. There is also the 

 risk in this procedure that the water will not stop at the edge of the 

 slide but will flood off it unexpectedly, carrying the sections with it onto 

 the surface of the hot plate. 



Another procedure, which is not recommended for the inexperienced, 

 is to blot the sections before putting them on the hot plate. If one takes 

 the slide after the water has been drained from it and lays on its surface 

 a water-saturated piece of coarse filter paper, one can then press hard 

 on the paper with a rubber roller, squeezing much of the water out of 

 both the paper and the sections. This assures that the sections are per- 

 fectly flattened in contact with the slide, but requires strong nerves to 

 try for the first time because of the fear that the sections will stick to the 

 paper. This has not happened in a good many thousand slides which the 

 author has made by this means, and slides so prepared are always free 

 of air bubbles. 



Before proceeding to a discussion of the next steps to be taken, it may 

 be well to review the innumerable things that may happen to prevent 

 the production of a perfect ribbon. The appearance, cause, and cure of 

 the more common defects are shown in Table 2. These are by no means 

 the only defects or the only cures that may be applied and every user 

 of the microtome should have in his hands O. W. Richards' "The Effec- 



