APPENDIX. — STAINING FLUIDS. 213 



sufficient quantity to produce the requisite depth of color. This form is pref- 

 erable to the one above described for use with methyl-blue for the double stain- 

 ing of tissues, but is not so useful for the study of protoplasm and the nucleus. 



Preparations stained with carmine may be permanently mounted in Canada 

 balsam or in Hoyer's fluid for carmine, but not in glycerine jelly. 



Grenacher's Haematoxylin Solution. Prepare a saturated solution of 

 haematoxylin in absolute alcohol and, in another vessel, a saturated solution of 

 ammonia alum in distilled water. Mix the two solutions in the proportion of 

 two parts of the former to seventy-five of the latter. The solution should now 

 be allowed to stand in the light for a week, then filtered, and to every seven 

 parts of it one part each of glycerine and methylated alcohol are to be added. 

 After the solution has stood for some time it should again be filtered or 

 decanted in case a sediment has been deposited. 



Haematoxylin is one of the most useful of stains. It stains both lignified 

 and cellulose tissues but not suberin or cutin. It is also one of the very best 

 nuclear stains. Old solutions are to be preferred, and the best results are 

 obtained when they are used very dilute. Acids are incompatible with this 

 stain. As we have already seen, a % per cent, solution of hydrochloric acid in 

 70 per cent, alcohol may be used to remove a part of the coloring from over- 

 stained sections. Sometimes beautiful results are obtained by this means, as 

 some tissues part with the staining material more readily than others. The 

 stain does not work well with preparations that have been kept for a long time 

 in alcohol. Both alcoholic and picric acid preparations should be very thor- 

 oughly washed in water before staining in this solution. Either Canada bal- 

 sam or glycerine jelly may be used as a mounting medium. 



Methyl-Green. Dissolve enough methyl-green in distilled water to com- 

 municate to the liquid a deep green color. It stains lignified and cutinized 

 tissues more readily than those composed of pure cellulose. The tissues take 

 up the stain more readily if they are previously washed with water slightly 

 acidulated with nitric acid. 



Acetic Methyl-Green, which consists of a one or two per cent, solution 

 of glacial acetic acid in distilled water, in which methyl green is dissolved until 

 a clear blue-green color is pioduced, is serviceable for fixing and staining the 

 nucleus, but the color thus obtained is not permanent. 



Eosin Solution. A strong alcoholic solution is particularly useful in the 

 study of sieve-tissues, as it stains the thin albuminoid contents of the tubes a 

 deeper red color than the rest of the structure. It also stains protoplasm and 

 the nucleus. 



Safranin, dissolved in absolute alcohol, is serviceable as a nuclear stain in 

 the case of specimens which have been hardened in alcohol or in picric acid 

 solution. If hardened in the latter solution thorough washing in water is 

 necessary before applying the stain. Sections should be left in the staining 

 solution for from twelve to twenty-four hours, and then washed in absolute alcohol 

 until the color is mostly removed from the cell walls, when the nuclei will be 

 found to be finely stained and their structure clearly visible. The sections 

 should now be transferred for a short time to oil of cloves and then mounted 

 in balsam. • 



