MoiDiliiig 57 



labeled "Cleaned, ready for use," save many technician hours devoted 

 to cleaning the uncleaned varieties. In addition, they permit a imiform 

 smear for blood smears and the like. 



Cover glasses are manufactured in circles, squares and rectangles, in 

 thickness ranging from #0 to #3. Thickness #0 is used rarely, when 

 an oil immersion objective rides imusually close to the slide. This size 

 is so thin that it fractures easily. Thickness :f^l (about 0.15 mm.) usu- 

 ally is adequate for oil immersion ^vork. Thickness #2 (about 0.20 mm.) 

 can be used for Avhole mounts or when oil immersion is tmnecessary. 

 Thickness ^3 (about 0.30-0.35 mm.) is occasionally used when a 

 tougher glass is required and for large whole moimts. Circles and 

 squares are purchasable in sizes up to | inch in diameter. Circles are 

 designed for mounts when ringing the cover is necessary. Whole mounts 

 in glycerol jelly or any other \olatile mountant must be sealed against 

 evaporation. A ringing table can be used to make the supporting ring 

 for the co\ er glass and then the final seal around the edge of the cover 

 glass. The rectangles come in 22 and 24 mm. widths, and in 30, 40, 50 

 and 60 mm. lengths. Cover glasses will mount more efficiently if they 

 are cleaned in absolute alcohol and wiped dry. Fewer bubbles cling to 

 the glass when it is pressed into place over the moimting medium. 



Moiintiyig Technics 



If paraffin sections are to be stained imiformly, the embedding solution 

 is removed, but the sections could lose their unity if they are not affixed 

 to the slides. Also moimting on slides permits handling of many sections 

 simultaneously, as is desirable for serial sections. 



Before sections are moimted, a glass marking pencil should be used 

 to inake an identifying mark on one end of the slide — a tissue number, 

 student locker number, research project number or a similar identifica- 

 tion to prevent confusion with other slides. In addition, this enables the 

 worker to distinguish on ^vhich side of the slides the sections are mounted 

 and thus prevent failure during the staining process. Types of permanent 

 glass marking pencils include diamond points (a real commercial dia- 

 mond mounted in a handle) and steel pencils with tungsten-carbide tips 

 {Fisher Scientific Company ^13-378). A vibro-engraver or vibro-tool 

 can be used for engraved marking on the glass. Wax cliina-marking 

 pencils make only temporary inscriptions which dissolve in the staining 

 solutions. Soine inks are reasonably satisfactory; one of the best is Gold 

 Seal Laboratory Ink [:^A-l-iOS, Clay-Adams, Inc., N.Y.). Stafford {I960) 



