Staining Animal Sections. 79 



and 3 drams of glacial acetic acid. The mixture must now 

 be left exposed to light for at least a month, then filter, and 

 keep in a stoppered bottle. 



Staining Process. (1) If the specimen has been har- 

 dened in any of the chromic solutions, place the section in 

 a 1 per cent, watery solution of bicarbonate of soda for 

 about five minutes, then wash well in distilled water. If it is 

 a spirit preparation the soda will not be required, but all 

 sections must be washed in distilled water before they go 

 into logwood stain. 



(2) To a watch-glass full of distilled water add from 10 to 

 20 drops of the logwood solution, and immerse the section 

 for frbin ten to thirty minutes. 



(3) Wash in distilled water, then in ordinary tap water ; 

 the latter will fix the dye and cause the colour to become 

 blue. 



(4) Dehydrate in methylated spirit. 



(5) Clear in clove-oil, and mount in Canada balsam. 

 Double Staining with Logwood and Rosin. Stain 



the section in hsematoxylin, as directed above ; then place 

 it in an alcoholic solution of rosin, about 1 grain of rosin 

 to an ounce of methylated spirit is strong enough, and let 

 it soak for about five minutes ; wash well in methylated 

 spirit, clear in clove-oil, and mount in Canada balsam. 



Mounting in Canada Balsam. Take 3 ounces of dried 

 C. balsam and dissolve in 3 fluid ounces of pure benzol, 

 filter, and keep in an outside stoppered bottle. Clear the 

 section in clove oil, and place it in turpentine. Clean a 

 cover-glass and a slide, place a few drops of balsam on the 

 centre of the latter, take the section from the turpentine on 

 a lifter, allow the excess of turpentine to drain away, and 

 with a needle-point pull the section off the lifter into the 

 balsam on the slide. Now take up the cover-glass with a 

 pair of forceps, and bring its edge in contact with the 

 balsam on the slide ; ease it down carefully, so that no air- 

 bubbles are enclosed, and with the points of the forceps 

 press on the surface of the cover until the section lies quite 



