CHAPTER XIII. 149 



242. HEIDENHAIN'S Iron Hsematoxylin (M. HEIDENHAIN, " Uber 

 Kern und Protoplasma," in Festschr. fur Kolliker, 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 always meant in histology the double salt of 

 ammonium and sesquioxide of iron (NH 4 ) 2 Fe 2 (S0 4 ).i, 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, 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 haematoxylin. They 

 are then rinsed with water, and again treated with the iron solution, 

 which slowly washes out the stain. The progress of the differentia- 

 tion ought to be controlled under the microscope. The sections 

 should to this end be removed from time to time from the alum 

 solution, and put into tap-water whilst they are being examined. 

 This is favourable to the stain. As soon as a satisfactory differentia- 

 tion has been obtained, the preparations are washed for at least a 

 quarter of an hour in running water, but not more than an hour, 

 and mounted. The results differ according to the duration of the 

 treatment with the iron and the stain. If the baths have been of 

 short duration, viz. not more than half an hour in the iron and as 

 much in the stain, blue preparations will be obtained. These show 

 a very intense and highly differentiated stain of nuclear structures, 

 cytoplasmic structures being pale. If the baths in the iron and in 

 the stain have been prolonged (twelve to eighteen hours), and the 

 subsequent differentiation in the second iron bath also duly pro- 

 longed, black preparations will mult. These show chromosomes 

 stained, central corpuscles stained intensely black, cytoplasm some- 

 times colourless, sometimes grey, in which case achromatic spindle- 

 fibres and cell-plates are stained, connective-tissue fibres black, red 

 blood-corpuscles black, micro-organisms sharply stained, striated 

 muscle very finely shown. 



Later (Zeit. wiss. Mik., xiii, 1896, p. 186) Heidenhain gives further 

 instructions for the employment of this stain in the study of central 

 corpuscles. All alcohol should be removed from the tissues * by 

 means of distilled water before bringing them into the mordant. 



* Why ! I find my iron-alum solution, as well as the liquor ferri 

 sulph. oxid., last , mix clear with alcohol without the least precipitate 

 forming. 



