H^MATEIN (HjgMATOXYLTN) STAINS. 161 



either with very strong solutionSj or with the slow stain of 

 the dilute solutions^ is at the same time a plasma-stain, which 

 of course may or may not be desired. Mayee says that very 

 dilute solutions will give a pure nuclear stain if they have 

 been diluted with alum-solution, or have been acidified. 

 Chromosmium material will not yield a pure chromatin 

 stain unless it is very fresh ; it is consequently next to im- 

 possible to obtain the reaction with paraffin sections of such 

 material ; they constantly give a plasma-stain in addition to 

 the chromatin stain, which is not the case with sublimate 

 material. 



The stain is fairly permanent in balsam, but is very liable 

 to fade a little, and may fade a great deal. If acids have 

 been used after staining, great care should be taken to wash 

 them out thoroughly before mounting. In aqueous media the 

 stain cannot be relied on to keep (this refers to the old solu- 

 tions : Mayee finds that his htematein preparations have kept 

 well for at least some months in glycerin, if not acid, and, 

 with certain precautions, in balsam). Turpentine-balsam 

 should not be used. 



Formulae §§ 248 to 259 give aqueous solutions ; and 

 §§ 260 to 263 alcoholic ones. 



248. Mayee's Hsemalum, Newer Formula {Zeit. iriss. Mih., xx, 

 1903, p. 409). — Hsematox-ylin, 1 grm.; water, 1 litre. Dis- 

 solve, and add 0'2 grm. of iodate of sodium (NalOg) and 

 50 grms. of alum, dissolve and filter. 



TMs is an amended formula. The original one (MiWi. Zool. Stat. 

 Neapel, x, 1891, p. 172) was ; One grm. of hiematein (or the ammonia salt, 

 §§ 238, 239) dissolved with heat in 50 c.c. of 90 per cent, alcohol, and 

 added to a solution of 60 gr. of alum in a litre of distilled water. 



This solution does not keep very well, but may be made 

 more stable by adding 50 grms. of chloral hydrate and 1 grm. 

 of citric (or acetic) acid. 



It stains equally well, either at first, or later. Con- 

 centrated, it stains sometimes almost instantaneously, or in 

 any case very rapidly. (Spring water or tap-water contain- 

 ing lime must not be used for diluting ; perhaps weak 

 solution of alum in distilled water is the best means of all.) 

 After staining, sections may be washed out either with 



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