58 Paraffin Method (chap. 5) 



uses a waterproof pencil {Venus Unique Blue Waterproof Pencil 

 ^1206, American Pencil Co.) on slides with frosted ends, but this may 

 be removable in xylene or alcohol. 



The customary means of affixing sections to slides is attachment with 

 egg albumen and water. (Gelatine and blood serum also can be used, 

 page 414.) Absolutely clean slides are essential to insure adherence of 

 the sections throughout any staining procedure. With one finger smear 

 a thin film of albumen fixative (adhesive, page 412) on the slide, and 

 with a second finger wipe off excess albumen. This should keep the film 

 thin enough. Thick albumen picks up stain, makes a messy looking 

 slide, and can obstruct a clear image of sharp uncluttered tissue ele- 

 ments. If there is a continued tendency to get too much albumen on 

 the slide, try a "floating solution"; dilute a couple of drops of albumen 

 fixative with about 10 ml. of distilled water and float the sections on 

 the solution on the slide (also see Schleicher, 1951). Lillie {1954B) sug- 

 gests that since water is used to float the sections on a thin coat of fixa- 

 tive and since the fixative constituents are water soluble, it is doubtful 

 that enough albumen remains on the slide to actually be an adhesive 

 agent. He considers it probable that the albumen acts as a surface ten- 

 sion depressant and aids in closer attraction of sections to slide. 



If a water bath is used for spreading the sections, have the tempera- 

 ture of the bath about 5°C below the melting point of the paraffin 

 being used. When removing the sections from the microtome knife or 

 from the box, stretch them as flat as possible as they are placed on the 

 water surface. After they have warmed a bit, they can then be pulled 

 more nearly to their original size with a couple of dissecting needles. 

 With a hot needle or spatula separate the required sections from the 

 rest of the ribbon. Dip an albumenized slide under them and with 

 a needle hold them against the slide while removing it from the bath. 

 Drain off excess water and dry the slide on a warming table or in an 

 oven. Sections collected (glossy side down) in a box can be separated with 

 a spatula or razor and removed to an albumenized slide. Add enough 

 distilled water to spread well beyond the edge of the sections. Place the 

 slide on a slide warmer^ to correct any compression acquired during 

 sectioning and until the sections are stretched flat. Dense tissues will 

 compress less than the paraffin surrounding them and often will develop 

 folds because the paraffin does not expand sufficiently on the warm plate 

 to permit the tissues to ffatten. Pieces with a lumen will invariably dem- 

 onstrate this fault. One of the simplest ways to correct this difficulty is 

 to break away the paraffin from the outside edge of the tissue. Do this 



*One of the best is Fisher's Shde Warmer, Catalog 9^12-594-5. 



