H^EMATEIN (H^IMATOXYLIN) STAINS. 183 



A dark liquid of about the tint, at first, of borax-carmine, 

 becoming more blue- violet with time. It stains equally 

 well, either at first, for it is ripe from the beginning, or later. 

 Concentrated, it stains sometimes almost instantaneously, or 

 in any case very rapidly. Diluted twenty-fold with distilled 

 water it will still stain through the tentacles of a Tubularia 

 in an hour. (Spring water or tap-water containing 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 distilled or common 

 water. The solution is admira b le for staining in bulk. Large 

 objects will, however, require twenty-four hours' staining, and 

 should be washed out for the same time (this should be done 

 with 1 per cent, alum solution if a sharp nuclear stain be 

 desired). All alum must be carefully washed out of the 

 tissues before mounting in balsam ; and it is well to blue the 

 stain with tap- water or otherwise, 236. The solution un- 

 fortunately does not keep perfectly, but precipitates and 

 becomes weak with age. When this has occurred, it is well 

 to withdraw the quantity required for staining from the 

 middle of the stock solution by means of a pipette, which 

 should be wiped outside before allowing the liquid to run out 

 of it. The stain is generally a nuclear one ; in any case 

 such may be obtained by washing out with alum -solution. 

 Mayer's preparations have kept well in glycerin (care being 

 taken not to have it acid), also in balsam. It is to be noted 

 that if oil of bergamot be used for clearing, it must be 

 thoroughly removed by means of oil of turpentine before 

 mounting ; and that oil of cloves is dangerous. It is best 

 (Mayer, /// lift.) to use only xylol, benzol, or chloroform, 

 and to mount in xylol-balsam or chloroform-balsam or benzol- 

 balsam. 



Haemalum may be mixed with alum-carmine, Saurefuchsin, 

 or the like, to make a double staining mixture ; but it seems 

 preferable to use the solutions in succession. 



239. MAYER'S Acid Haemalum (ibid., p. 147, note). This 

 is haemalum with 2 per cent, glacial acetic acid (or 4 per 

 cent, common acetic acid). To be used as the last, washing 

 out with ordinary water in order to obtain a blue-violet tint 



