H.EMATEIN (H^MATOXYLIN) STAINS. 189 



This process is applicable to all sorts of organs, and gives 

 in particular excellent images of axis-cylinders, and of the 

 achromatic figure of cell-division. It is sometimes useful to 

 add a second stain with Saurefuchsin, or Bordeaux. If the 

 iron solution be taken for the differentiation, it should be 

 taken extremely diluted (of a very pale straw-colour), and 

 the progress of the differentiation watched ; as if it be only 

 diluted about tenfold, for instance, the decoloration is ex- 

 tremely rapid. 



The stain is nuclear or nuclear and plasmatic according to 

 the amount of differentiation, and is one of the most splendid 

 stains known. The tone varies somewhat between dark blue 

 and dead black (see next ). After most carefully com- 

 paring it with that of M. Heidenhain (next ) I find that in 

 result the two are absolutely identical, Benda's process having 

 the advantage that his Liq. fe. sulph. keeps indefinitely, 

 which Heidenhain' s ferric solution does not. Either of these 

 processes, when successful, gives a stain of an optical quality 

 that is peculiarly suited to the employment of high micro- 

 scopic powers, and will allow of the employment of deeper 

 eye-piece* than any other stain known to me. Both the pro- 

 cesses are somewhat crotchety, and 1 have met with material 

 with which it has been impossible to obtain the correct stain 

 (probably on account of some peculiarity in the fixation). 



255. Iron Haematoxylin (M. HEIDENHAIN, " Uber Kern und 

 Protoplasma," inFestschr. Herrn. Geheimr. A. v. Kolliker, etc., 

 gewidm., 1892, p. 118). Sections are treated from half an 

 hour to at most two or three hours with a 1'5 to 4 per cent, 

 solution of ferric alum (ammonio-ferric sulphate). By this 

 is meant the double salt of the sesquioxide of iron (NH 4 ) 

 Fe (S0 4 ) 4 , in clear violet crystals; the double salt of the 

 protoxide, or salt of MOHR in green crystals, will not serve. 

 If the crystals have become yellow and opaque, they have 

 gone bad, and should be rejected. They ought to be kept 

 in a stoppered bottle, and the solution should be made in the 

 cold (Arch,/, mik. Anat., xliii, 3, 1894, pp. 431, 435). The 

 sections are then washed with water and stained for half an 

 hour in an aqueous solution (of about 0*5 per cent.) of 

 hsematoxylin. (Ha3matoxyliii is stated by Heidenhain to 

 give better results than hasmatein.) They are then rinsed 



