CHAPTER XXVI. 323 



violet ( 330) diluted with an equal volume of water, and warm till 

 vapour is given off. Rinse, differentiate one or two minutes in 

 30 per cent, acetic acid (till the nuclei come out reddish), wash in 

 running water for five to ten minutes, dry with blotting-paper, dip 

 into absolute alcohol, pass through bergamot oil into xylol and 

 balsam. Mitochondria violet, chromatin and " archoplasm " brown- 

 red, certain secretion granules pale violet, centrosomes red 

 violet. 



Instead of the staining solution prescribed above (which may be 

 kept in stock) you may take (Encycl., ii, p. 198) a, freshly prepared 

 mixture of equal parts of anilin water and saturated alcoholic 

 solution of crystal violet and this is to be preferred. 



Some workers prefer to harden as BENDA, but to stain with iron 

 haematoxylin instead of by the alizarin process ; the special hardening 

 rendering the hsematoxylin stain sufficiently specific. 



ARNOLD (Arch. Zellf., viii, 1912, p. 256) stains first with iron hsema- 

 toxylin, differentiates, stains for twenty to thirty minutes with saturated 

 aqueous solution of thionin, passes up to absolute alcohol, stains for two 

 minutes with Orange G dissolved in clove oil, and passes through xylol 

 into balsam. Chromatin blue, chondriosomes black. 



684. Formalin-Chrome Techniques.* The methods of Regaitd, 

 Bensley-Cowdry, Schridde, Murray, etc., are of importance on 

 account of their suitability for vertebrate, and especially mammalian 

 tissues. The tissues are fixed either in neutral formalin or in 

 formalin-chrome mixtures, washed, and then mordanted in 3 per 

 cent. K 2 Cr 2 7 . As with Champy-Kull, it is possible to stain after 

 such fixation by a variety of methods : iron hsematoxylin, acid 

 fuchsin, alizarin and crystal violet, safranin, etc. The Regaud and 

 Bensley-Cowdry methods do not preserve neutral fat in the finished 

 sections, but by post-osmication, as for Schridde ( 687), or Murray 

 ( 689), this can be done. 



685. REGAUD'S Formol- Bichromate and Iron Haematoxylin (Arch. 

 d'Anat. micr., t. xi, 1910). Fix in a mixture of 3 per cent, potassium 

 bichromate 80 volumes, commercial formalin 20 volumes, for four 

 days, changing every day. Mordant in potassium bichromate for 

 seven days, changing every second day. Wash in running water 

 twenty-four hours, dehydrate (twenty-four hours each strength), 



* Note that formalin-chrome mixtures consist of a reducer and an 

 oxidiser, and will not keep. Such solutions should always be made up 

 just before use. Zenker's fluid, too, keeps better without the acetic acid, 

 which, if b.?ing used, should be added just before the material is put in 

 the fixative. 



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