MICROSCOPICAL TECHNIQUE. 89 



Stains for Vegetable Tissues.*— Dr. E. Vinassa has investi- 

 gated the value of aniHne colours for staining v;egetable tissues, 

 and divides them into three groups only : safranin, congo-red, 

 benzopurpurins, etc. ; those affecting lignified tissues, collenchyma 

 vessels, and nuclear sheaths — vesuvin, Victoria green, chrysoidin, 

 violet, methyl green, fuchsin, etc. ; and stains that merely differ- 

 entiate, such as Victoria blues B, RRRR, and BB, which colour 

 the thickened cells darker than the surrounding tissue, and thus 

 render them more conspicuous. To ensure sections being well 

 stained, all protoplasm, etc., must be got rid of. This is effected 

 with soda lye, washing with much water (acidified with acetic acid 

 if necessary), and then allowing to drain. Afterw^ards immerse in 

 a J to I per cent lukewarm stain solution for two or three minutes, 

 and again wash until the water runs clear. 



For double staining, first put sections in the stain affecting the 

 lignified tissue, thickened cell-walls, etc., wash well and transfer to 

 stain for parenchyma. This should be heated to loo C , and 

 rendered slightly alkaline. Colours which are fast on cotton were 

 found to stain parenchyma, whilst those that dye wool or silk 

 directly stain the thickened cell-walls, etc. Suitable mordants 

 (tannin, acetate of lead, etc.) for fixing the colours must be found 

 by experiment. 



Staining Tubercle Bacilli.t— A modification of Frankel's 

 method consists in dissolving r part of fuchsin in loo parts of a 

 5 per cent, solution of carbolic acid, adding lo per cent, of abso- 

 lute alcohol and heating the fluid in a watch-glass to near the 

 boiling point. Float the cover-glasses in the stain for two minutes, 

 remove, and vnmediately immerse for one minute in a solution of 

 one to two parts methylene blue in loo parts of 25 per cent, sul- 

 phuric acid. Then flood with water, dry, mount in balsam. 



Cements for Slides.— The "Gram-Rutzou " composition recom- 

 mended by Poulsem ( Bota7iical Micro-Che?nisiry) appears to grow 

 in favour. It consists of Canada balsam 50 gm., shellac 50 gm., 

 absolute alcohol 50 gm., and ether 100 gm. When mixed, dis- 



* From abstract in Microscopical Bulletin, VIII., 6, p. 41. 

 "^Merck's Bulletin, Vol. V., 3, p. 168. 



