82 MICROSCOPICAL TECHNIQUE. 



manner. The sections should be fixed to the slide with Schalli- 

 baum's collodion and not with Mayer's albumen, which discharges 

 the colour. Whole preparations or sections made in this way are 

 serviceable for study for several weeks ; but after an interval of a 

 month the finer details in them are likely to fade. 



" The principal difficulties met with in employing this method 

 are three : — A semi-crystalline condition of the precipitate, due, 

 apparently, to over-action of the corrosive sublimate ; incomplete 

 dehydration and imperfect removal of the corrosive sublimate. 

 Remedies for these troubles easily suggest themselves. 



" The essential steps in the method can be recapitulated as 

 follows, the lengths of time given being those required for a satis- 

 factory preparation of a ganglion in the ventral nerve-chain of the 

 crayfish : — 



I. — Cold, saturated, aqueous solution of corrosive sublimate 

 for lo minutes. 



2, — Solution A : — Methylal, 5 ccm. ) corrosive sublimate, i gr. ; 

 for fifteen minutes. 



3. — Solution B : — Methylal, i vol. ; solution A, i vol. ; xylol, 

 2 vols. ; for ten minutes. 



4. — Pure xylol in considerable quantities for 4 or 5 days. 



5. — Mount preparation in xylol-balsam, or embed in paraffin 

 and cut sections." 



An Aqueous Solution of Hsematoxylin which does not readily 

 deteriorate."^ — Prof. S. H. Gage — finding that aqueous solutions of 

 hgematoxylin soon begin to deposit a dark precipitate on the bottle 

 and become filled with granules and mycelium growths — has 

 devised the following solution, which, after a lapse of eight months, 

 is as good as when first made : — Distilled water, 300 cc. ; Potash 

 alum, 10 grams; Chloral hydrate, 6 grams; Hsematoxylin crystals, 

 i/ioth gram. Place the water in a porcelain dish, add the alum 

 either in powder or small pieces, and boil for five minutes. When 

 cool, add the chloral hydrate and the haematoxylin. It is advan- 

 tageous to dissolve the haematoxylin in 5 to 10 cc, of absolute or 

 95 per cent, alcohol before adding to the alum solution. 



The colour is quite light at first, but afterwards changes to a 



* Read before the American Micros. See, 1892. Micros. BuL, ix. (1892), 

 PP- 36, 37- 



