MICROSCOPIC STUDY AND STAINING 111 



NicoUe advises the use of a ten per cent aqueous solution of tannic 

 acid for a few seconds after washing with the acetic acid. This fixes 

 the stain and prevents a too vigorous decolorization during the process 

 of dehydration. 



Method of Staining Gkam-Positive Bacteria in Tissue Sections. 

 — Celloidin Sections. — After fixing section to the slide by pressure with 

 a filter paper or by ether vapor, cover with anilin-water gentian-violet 

 five minutes. 



Pour off excess of stain and cover with Gram's iodin solution for 

 two minutes. 



Decolorize with ninety-five per cent alcohol until no more color 

 comes out. 



Stain quickly with eosin-alcohol (ninety-five per cent alcohol to 

 which enough eosin has been added to give a transparent pink color; 

 about 1 : 15). Clear in eosin-oil of origanum (oil of origanum, 25 c.c. 

 and eosin alcohol, as above, about 3 c.c). 



Blot and mount in balsam. 



Paraffin Sections. — Stain with anilin-water gentian-violet five to tet 

 minutes. 



Wash in water. 



Cover with Gram's iodin solution one minute. 



Wash in water. 



Decolorize with absolute alcohol until no more color comes out. 



Clear in xylol. 



Mount in balsam. 



Gram-Weigert Method.^ — (For celloidin sections.) — Stain for one-half 

 hour in the following freshly filtered solution: 



Carmine 3-5 grams. 



Saturated aqueous solution of lithium carbonate. . . .100 c.c. 



Dehydrate in ninety-five per cent alcohol. 



Stick section to slide with ether vapor. 



Stain in anilin-water gentian-violet for five to fifteen minutes (or 

 n a saturated solution of aqueous crystal violet diluted with water 

 one to ten, five to fifteen minutes). 



Wash in physiological salt solution. 



Cover with Gram's iodin solution one to two minutes. 



Wash in water and blot. 



> Weigert, Fortschr. d. Med., v, 1887. 



