and mount in balsam. This may be used alone to give a blue stain with tissue 

 fixed in Hermann's or Flemming's fluid. 



$ 91. Methyl green. This is an nuclear stain of much value, besides 

 being an important ingredient of triple stains (e.g., Ehrlich's triacid mixture). 

 In very dilute solutions it is serviceable in staining the nuclei of fresh tissue 

 and of isolated cells (formula below). A i% aqueous solution is used with 

 hematoxylin and picrofuchsin in differentiating the structure of the hair folli- 

 cle. (See 1 54). 



92. Methyl green and eosin. Formulas: (a) Aqueous solution. i% 

 aqueous solution of methyl green, \y 2 c.c. ; %% aqueous solution of eosin, i 

 c.c. ; normal salt solution, 100 c.c. 



(b) Glycerin solution (for mounting). i% aqueous solution of methyl 

 green, 2 c.c. ; V 2 % aqueous solution of eosin, I c.c. ; glycerin, 100 c.c. 



These solutions may be used for staining isolated cells ; formula (a) for 

 temporary examination, formula (b) as a mounting and staining medium 

 combined. 



$ 93. Ehrlich's triacid mixture. Formula : Saturated aqueous solution 

 of orange G, 12 c. c. ; saturated aqueous solution of acid fuchsin, 8 c. c.; sat- 

 urated aqueous solution of methyl green, 10-12 c. c.; distilled water, 30 c. c. ; 

 alcohol (95% -j- ), 18 c. c. ; glycerin, 5 c. c. Mix the orange G and acid fuchsin 

 and add drop by drop, or a few drops at a time, the solution of methyl green, 

 stirring or shaking between each addition ; then add the alcohol, water, and 

 glycerin. Shake thoroughly and allow the mixture to stand for 24 hours. Do 

 not filter or shake, but take the stain from the bottle by means of a pipette. 



Stain sections for 10-15 minutes, rinse off the superfluous stain with dis- 

 tilled water and dehydrate and clear as quickly as possible ; this is necessary 

 since the alcohol washes out the methyl green (nuclear stain) very rapidly. 

 This stain colors collodion very deeply, hence it cannot well be used with col- 

 lodion sections. It affords a good and often valuable stain. The sections 

 should, however, beihin, and dehydration must be rapid. For the use of the 

 mixture in staining blood films, see \ 125. 



$94. Eosin. Formulas: (a) y 2 % aqueous solution; (b) 2% aqueous 

 solution ; (c) ^% solution in water or 50% alcohol. Formula (a) is prefera- 

 ble for most work; (b) affords a stronger and (c) a weaker stain. This may 

 be used as a counter-stain with hematoxylin to differentiate nucleus from 

 cell-body. Stain sections after hematoxylin for 10-30 seconds, wash away the 

 excess of stain with distilled water or 6j% alcohol. Since alcohol tends to 

 wash out the eosin, unless the color is too strong it is advisable to hasten the 

 process of washing out and dehydration. 



^95. Erythrosin. Formulas: (a) l / 2 -i% solution in 67% alcohol, (b) 

 y 2 -\% aqueous solution, ( c) ^% aqueous solution. This is a general stain sim- 

 ilar to eosin in its staining properties, but gives a redder color. Formulas (a), 

 and (b) may be used with sections and in the same way as eosin. Formula (c) 

 is used with tissues dissociated in formaldehyde dissociator. 



\ 96. Picric alcohol (acid). Formula: Picric acid, .2 grams; distilled 



