326 CHAPTER XXVI. 



It is said by Heidenhain that the stain is obtained in a sharper form 

 by combining the liasmatoxylin stain with a foregoing stain with 

 Bordeaux B. He directs (Arch. mile. Anat., xhi, 1894, p. 665) that the 

 sections (sublimate sections were used by liim) are to be stained for 

 tvventy-fom- hours or more in " a weak " solution of Bordeaux, until they 

 have attained such an intensity of colour as that " they would just be fit 

 for microscopic examination with high powers " {I. c, p. 440, note), and 

 that they be then brought into the ferric alum. After mordanting and 

 staining, the hsematoxylin is to be extracted in the iron alum until the 

 chromatin has become entirely or almost entirely colourless. Instead 

 of Bordeaux, " anilin blue " may be used in the same way. 



The images of these objects given by iron-hsematoxylin 

 require to be interpreted with special care. For they 

 sometimes exhibit the phenomenon termed by Fischer 

 {Fixirung, Fdrhung und Bau des Protoplasmas, 1899^ p. 31, 

 et p"sswO " Spiegelfaerbung," that is — a hull's eye effect. 

 Globular or even elongated objects, such as chromosomes, do 

 not always yield up their stain simultaneously and equally 

 throughout their whole depth, but lose it suddenly and 

 entirely in their outer layers, whilst retaining it in its full 

 strength in their deeper layers. The still-stained parts thus 

 remain separated from the decoloured parts by a sharply- 

 defined limit ; so that a spherical granule in this state will 

 show a central point deeply stained — the bull's eye — and 

 around it a perfectly colourless area — the white of the target. 

 And when the object is in balsam it is frequently quite 

 impossible to distinguish the outer limit of this colourless 

 area, so that the whole object appears to have only the 

 dimensions of the stained area. It seems that certain 

 erroneous observations that have been published have been 

 due to this deception. 



Hbemann {Arch. mih. Anat., xxxvii, 4, 1891, p. 583) I'ecommends a 

 modification of the hsematoxylin impregnation method of Pal, for which 

 see fourth edition ; also his paper, " Methoden zxim Studium des Ai'cho- 

 plasmas " in Ergehnisse^der Anatomie, Band ii, 1892 (1893), p. 23. 



For Heidenhain's Vanadium hiematoxylin, see § 269. 



Benda (Verh. Bhys. Oes. Berlin, November, 1900, Nr. 1-2; Verh. 

 Anat. Ges., xv, 1901, p. 167) gives the following as succedanea of the 

 iron hajmatoxylin method : The material is to be fixed in alcohol of 

 about 93 per cent, for two days, then treated for twenty-four hours with 

 nitric acid diluted with 10 vols, of water. Then bichi-omate of potash 

 of 2 per cent., twenty-four hours ; chromic acid of 1 percent., forty-eight 

 hours ; water, twenty-four hours ; alcohol ; paraffin (or sections by 



