26 



THE ART OF MAKING MICROSCOPE SLIDES 



Deep cells 



time of making the slide and to turn an 

 additional coat on top every two or three 

 years. Slides treated in this manner may 

 be kept for as long as 20 years without 

 any air bubbles appearing. The petroleum 

 jelly method of Spence, which in the 

 author's opinion is more applicable to 



Drop of preservative 

 Object 



to the side of the cell or dissolved in the 

 mounting medium. It is best to remove 

 dissolved air from the medium either by 

 boihng or by placing a small beaker of the 

 medium under a vacuum until all the 

 dissolved air has been removed. A pro- 

 tective ring is turned as before (Fig. 15) 



Gold size ring 

 Cell 



15 



Coverslip 



X 



16 



Preservative 

 withdrawn 



ML 



17 



Gold size sealing 

 coat 



18 



Asphalt varnish 

 finishing coat 



19 



Figs. 15 to 19. Sections showing successive stages in the preparation of an aqueous 

 wholemount in a deep cell. 15. The cell has been cemented to the slide, and a gold size ring 

 turned on its inner edge, before being filled with fluid. 16. The coverslip is slid into position. 17. 

 Coverslip pushed into place and preservative withdrawn between gold size ring and edge of cover- 

 slip. 18. Heavy sealing coat of gold size applied. 19. Finishing coat of asphalt varnish applied over 

 gold size. 



glycerol than to aqueous mounts, is 

 given in the next chapter. For a descrip- 

 tion of a modification of this method ai> 

 plied to aqueous mounts, refer to Spence 

 1940 (il/icroscope, 4:121). 



The method of mounting in a relativel}' 

 deep cell is shown in Figs. 15-19. Par- 

 ticular care has to be taken in this case to 

 prevent the appearance of air bubl)les 

 which may come from air either attached 



but it will he seen, in this case, that this 

 protective ring is on the inner edge of the 

 upper surface of the cell. The cell is then 

 filled with the preservative fluid, allow- 

 ing an excess to rise in a concave meniscus. 

 To make sure that no air is caught on the 

 irregular surface of the inside of the cell 

 one may now either place the whole 

 under a vacuum or, more conveniently, 

 take a clean brush and wipe the inside of 



