308 GOLGI BODIES ETC. 



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 {Enzyk., 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. 



Dr. John Baker informs us that the following three suggestions 

 may be found helpful : — 



1. Cut very thin sections, the thinner the better. 



2. Add 3 drops of 1 per cent, calcium acetate solution (aqueous) 

 to the slide-bottle containing the alizarin solution. This favours 

 the action of the stain. 



3. While differentiating with acetic acid, disregard the interior 

 of the piece completely and concentrate the attention on the part 

 that has been well fixed by the osmium. 



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

 haematoxylin instead of by the alizarin process ; the special hardening 

 rendering the haematoxylin stain sufficiently specific. 



Arnold [Arch. Zellf., viii, 1912, p. 256) stains first with iron haema- 

 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. 



698. Formalin-Chrome Techniques.* The methods of Regaud, 

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

 account of their suitability for vertebrate, and especially mam- 

 malian tissues. The tissues are fixed either in neutral formalin 

 or in formalin-chrome mixtures, washed, and then mordanted in 

 3 per cent. KaCrgO.^ As with Champy-Kull, it is possible to stain 

 after such fixation by a variety of methods : — iron haematoxylin, 

 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 

 (§ 702), or Murray (§ 704), this can be done. 



699. 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), clear and imbed in paraffin. 

 Pass sections on slide down to water ; 5 per cent, iron alum at 



* 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 being used, should be added just before the material is put in 

 the fixative. 



