84 CYTOLOGICAL TECHNIQUE 



Thin sections for electron microscopy are usually cut with 

 knives made by breaking a piece of plate glass along a line at an 

 angle of 45° to one of its edges. "^ The cutting edge is the one at 

 the intersection of the two surfaces that subtend an angle of 

 45° to each other. 



Methacrylate sections may be stuck to glass slides for study 

 by phase-contrast microscopy (p. 128) in the same way as paraffin 

 sections. 2^ They are brought from 70% ethanol to water, and 

 floated on very dilute albumen solution on a glass slide. To re- 

 move the embedding medium after the section has been attached, 

 it is only necessary to put the slide in ethyl acetate or toluene, 

 which dissolves the polymer. The slide is then passed through the 

 usual series of ethanols to distilled water, and mounted in diluted 

 glycerol (p. 128). 



